


(Human avian) Rectusincesseris volant

by PinkIsopod85 (PinkAxolotl85)



Series: Technically Scientifically [1]
Category: Original Work
Genre: All mature sections are marked and you can choose to skip, Biology, Birds, Feel free to read and comment though, Human avians, Original World, Posted here mainly as a backup I don't expect anyone to see it, Science, Winged Humans, Wingfic
Language: English
Status: Completed
Published: 2018-03-09
Updated: 2018-05-14
Packaged: 2019-03-29 04:59:49
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 19
Words: 26,424
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13919880
Author URL: https://archiveofourown.org/users/PinkAxolotl85/pseuds/PinkIsopod85
Summary: "Despite advances in surgical technique that could theoretically lead to the ability to construct wings from arms, it is evident that humans should remain human, staying on the ground pondering and studying the intricacies of flight while letting birds be birds and angels be angels."Let's revise the human body to see if we can change that then.Please read revised version here





	1. [0] Taxonomy

**Author's Note:**

> I DON'T ACTUALLY EXPECT ANYONE TO READ THIS I'M JUST TERRIFIED OF LOSING THE WRITING BECAUSE I'VE ALREADY LOST PART OF IT SO I'M SHOVING IT HERE, OKAY? OKAY.
> 
> This world is a more ‘realistic’ one, or as realistic as you can get with winged humans. Avians are not just people that I’ve taped wings onto, explained they have hollow bones and called it a day. I've tried to make it as scientifically accurate as possible.
> 
> They have different instincts, posture, evolution, bone, and muscle structure, they have tailfeathers and feathers that aren’t just confined to the wings. I tried to meld ‘flight capable’ and ‘still humanoid’ together the best I could to create these guys. It’s also me trying to create a realistic culture and world for people with wings, not everything will be the same. One thing that’s not stated: Avians filled the same ecological niche that birds did and currently do. Things such as lizards and small mammals do everything birds would do now. So, if you’re inside this universe there are NO BIRDS only bats and flying lizards. Avians are also not considered mammals since they evolved from dinosaurs like birds did. Avians are not ‘human’ they are humanoid, they evolved from a Troodon and are not mammals.
> 
> This is written in an IN-UNIVERSE STYLE like a researcher compiling all the data they have on their own species. So, it will not be comparing avians to ‘humans’ since to them humans like us don’t exist. This is a completely open idea and you can use whatever I’ve stated here in your own stuff. I didn’t create the idea of a winged human, I just tried my best to refine it.
> 
> Based on this [Creature-Race creation form.](https://sethian-motzart.deviantart.com/art/Creature-Race-creation-sheet-314089755)

**         Medical Biology for _Rectusincesseris volant_ **

**         [0] Etymology **

_Rectusincesseris volant_ : Is their scientific name. It stands for ‘Upright flyers’ or more accurately ‘They fly upright’.

**Flighted** ( **s** ): This is the term used to refer to an avian that is capable of flight.

**Flightless** : This is the term used to refer to an avian that is not capable of flight, whether through their natural breeds or caused through injury.

**Avian** ( **Avia** ): This is the terms used to refer to one of the species, an avian. It is also the term used to refer to an adult.  (Person, people)

**Subadult** ( **s** ): This is the term used to refer to an adolescent avian, fully grown flight feathers, capability of flight but without full adult colouring. (Teenager, Teenagers.)

**Fledgeling** ( **s** ): This is the term used to refer to a young to adolescent avian, moulting down and growing flight feathers, but before capability of flight. (Child, Children.)

**Nestling** ( **s** ): This is the term used to refer to a young avian which has not yet started moulting their down. (Toddler, Toddlers.)

**Hatchling** ( **s** ): This is the term used to refer to a newly born avian and ones which have not yet grown down. (Baby, babies.)

 

 

**         [0.1] Family **

**Kingdom:** Animalia

**Phylum:** Chordata

**Clade:** Ornithurae

**Class:** Aves

**Notes for the Chapter:**

> Short but sweet.


	2. [1] Species

**          [1] Species **

The fossil record indicates that flighteds evolved from the feathered theropod group, which are traditionally placed within the saurischian dinosaurs. DNA-based evidence finds that flighteds diversified dramatically around the time of the extinction event 66 million years ago, which killed off the pterosaurs and most other dinosaur lineages.

They are characterized by an erect posture and primarily bipedal locomotion; high manual dexterity and relatively heavy tool use compared to other animals; and a general trend toward larger, more complex brains and societies.

Advantages that explain this success include a relatively larger brain with a particularly well-developed neocortex, prefrontal cortex and temporal lobes, which enable high levels of abstract reasoning, language, problem-solving, sociality, and culture through social learning. Avia use tools to an extremely high degree, are the only extant species known to build fires, clothe themselves, create, and use numerous technologies and arts.

Avia are uniquely adept at using systems of symbolic communication for self-expression, exchanging of ideas, and for organizing themselves into purposeful groups. Avia create complex social structures composed of many cooperating and competing groups, from families and kinship networks to political states.

Social interactions between avia have established an extremely wide variety of values, social norms, and rituals, which together form the basis of avian society. Curiosity and the avian desire to understand and influence the environment and to explain and manipulate phenomena has provided the foundation for developing numerous fields of knowledge.

Most of avian existence has been sustained by hunting or gathering in band societies. Increasing numbers of avian societies began to practice sedentary agriculture, domesticating plants and animals, thus allowing for the growth of civilization.

These avian societies subsequently expanded in size, establishing various forms of government, religion, and culture around the world, unifying avia within regions to form states and empires. The spread of avia and their large and increasing population has had a profound impact on large areas of the environment and millions of native species worldwide.

The rapid advancement of scientific and medical understanding in the 19th and 20th centuries led to the development of fuel-driven technologies and increased lifespans, causing the avian population to rise exponentially.

Today the global avian population is estimated to be near 8.2 billion.

**Notes for the Chapter:**

> I hope I haven't scared you off yet :p


	3. [2] Body description

** [2] Body description **

** [2.0] Typical **

The typical height of an adult avian is between 5ft and 6.9ft when standing upright without their hunch, although this varies significantly depending, among other things, on sex and ethnic origin. Body size is partly determined by genes and is also significantly influenced by environmental factors such as diet, exercise, avian species, and sleep patterns. Adult height for each sex in an ethnic group approximately follows a normal distribution.

Avians are considered an extremely light species. This is due to their ability of flight.

 

[2.0.0] Dimorphism / Structure of variation

Females on average are 10% heavier and 3inches taller than males, though in some species groups this is reversed. There is a difference between body types, body organs and systems, hormonal levels, sensory systems, and muscle mass between sexes. As there are chromosomal differences between females and males, some X and Y chromosome related conditions and disorders only affect either men or women. Other conditional differences between males and females are not related to sex chromosomes. Even after allowing for body weight and volume, the male voice is usually an octave deeper than the female voice.

Males typically have larger tracheae and branching bronchi, with about 15% greater lung volume per unit body mass. They have larger hearts, 10% higher red blood cell count, and higher haemoglobin, hence greater oxygen-carrying capacity. They also have higher circulating clotting factors. These differences lead to faster healing of wounds and higher peripheral pain tolerance. Females typically have more white blood cells (stored and circulating), more granulocytes and B and T lymphocytes. Additionally, they produce more antibodies at a faster rate than males. Hence, they develop fewer infectious diseases and these continue for shorter periods. Sexual dimorphism is incredibly high among males and females, females are typically larger, but males almost always have more colourful and intricate feathering.

**Notes for the Chapter:**

> Short, but it leads to a longer next chapter.


	4. [3] Body and shape

** [3] Body and shape **

** [3.0] Head / Skull **

[3.0.0] Shape

A flighteds skull is a bony structure that forms the head of the avian skeleton. It supports the structures of the face and forms a cavity for the brain. Like the skulls of other vertebrates, it protects the brain from injury. Their long neck is connected to the back of the skull.

Flighted avians have a slightly smaller and sloped skull, larger eye sockets and a sagittal crest. A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull. The presence of this ridge of bone indicates that there are exceptionally strong jaw muscles.

The facial skeleton is formed by the bones supporting the face. The mouth of the face slightly extends outwards to fit large teeth and more muscles to result in a stronger bite.

 

[3.0.1] Nose

The visible part of a flighteds nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the nasal bones and the nasal cartilages, including the septal cartilage (which separates the nostrils) and the upper and lower lateral cartilages. Small feathers run down the sides of the nose this is used to help flow air away from the eyes. The nose has an area of specialised cells which are responsible for smelling. Another function of the nose is the conditioning of inhaled air, warming it and making it more humid. Hairs inside the nose prevent large particles from entering the lungs. Sneezing is an automatic reaction caused by foreign particles irritating the nasal mucosa.

Since they generally have a poor sense of smell, the olfactory chamber is small, although it does contain three turbinates, which sometimes have a complex structure similar to that of mammals. In many avians, including doves and fowls, a horny protective shield covers the nostrils. The vomeronasal organ of flighteds is either under-developed or altogether absent, depending on the species.

 

[3.0.2] Eyes

Vision is the most important sense for avians, since good eyesight is essential for safe flight, and this group has a number of adaptations which give visual acuity superior to that of other vertebrate groups. The avian eye resembles that of a reptile, with ciliary muscles that can change the shape of the lens rapidly and to a greater extent than in the mammals. The eye's internal anatomy is similar to that of other vertebrates but has a structure, the pecten oculi, unique to avians.

The eyelids of an avian are not used in blinking. Instead, the eye is lubricated by the nictitating membrane, a third concealed eyelid that sweeps horizontally across the eye. The nictitating membrane also covers the eye and acts as a contact lens in many aquatic avians when they’re underwater. Avians can actively control their nictitating membrane. In fast flight or dives, they will blink repeatedly with their nictitating membranes to clear debris and spread moisture across the eyes.

Mainly diurnal species of avians have a ring of dark feathers that run around the eye. Almost all avians can control the size of their pupil, though it can still shrink and enlarge naturally due to bright light or darkness.

 

[3.0.3] Ears

The outer ear includes the pinna (the part that is made of cartilage and covered by small feathering) and the ear canal. The hearing of an avian varies from dull to incredibly sensitive – one can normally make an accurate guess as to which using the size, shape and feathering patterns as a guide. The pinna is shaped to capture sound waves and funnel them through the ear canal to the eardrum. The pinnae are mobile and can move independently of each other, allowing avians to locate multiple sounds at the same time. Often, the eyes are looking in the same direction as the moving ear is directed.

The ears of vertebrates are placed somewhat symmetrically on either side of the head, an arrangement that aids sound localisation. When in flight they do not often need to carefully listen, relying on eyesight instead. The ears are normally pressed down and flat against the head/neck and are normally kept there by the wind. However, even then they can still hear.

Most avians have their ears covered with tiny feathers specially designed to cut down on wind noise while permitting sound waves to pass through. These feathers behave like the foam covers sometimes seen on microphones. Some diving avians, such as penguins, have strong feathers covering their ear and pinna, to protect their delicate inner ears from intense water pressure.

 

[3.0.4] Mouth

In avian anatomy, the mouth is the first portion of the alimentary canal that receives food and produces saliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth. The mouth consists of two regions, the vestibule and the oral cavity proper. The mouth, normally moist, is lined with a mucous membrane and contains the teeth. The lips mark the transition from mucous membrane to the skin, which covers most of the body.

In addition to its primary role as the beginning of the digestive system, in avians, the mouth also plays a significant role in communication. While primary aspects of the voice are produced in the throat, the tongue, lips, and jaw are also needed to produce the range of sounds included in the avian language.

 

[3.0.5] Other features

The crest is a prominent feature exhibited by several avian species groups.

The crest is made up of semiplume feathers: a long rachis with barbs on either side. These are plumulaceous feathers, meaning that they are soft and bendable. In avians, these semiplumes are common along the head, neck, and upper back, and may be used for sensing vibrations or more commonly for displays.

Crests on avians are generally used for display purposes. Cockatoos and cockatiels, are part of the parrot family Cacatuidae found in Australia, the Bismarck Archipelago, and the Philippines, and are probably the most recognizable flighteds to feature crests. Cockatoos and cockatiels possess crests which may be raised or lowered at will. Their crests are used to communicate with fellow members of their species. Crests can be recumbent or recursive, depending on the species. The recumbent crest has feathers that are straight and lie down essentially flat on the head until the avian fans them out to where they stand up. The white cockatoo, for example, possesses a recumbent crest. The recursive crest is noticeable even when it is not fanned out because it features feathers, that, when lying down, curve upward at the tips, and when standing up, often bend slightly forward toward the front of the head. Many recursive crests also feature brilliant colours.

Crests mainly describe an abnormally long or colourful part of the hair commonly seen at the front of the head. This part came sometimes be finely controlled. The rest of the top of the head is covered in ‘hair feathering’. Hair feathering is shorter more fluffy feathers that grow much faster than the crest. They can be the same colour as the crest or much duller. This is the same for their eyebrows.

 

 

** [3.1] Neck **

A flighteds natural posture is slouched, this is due to multiple vertebrae along the spine and neck. Their neck and back can sometimes look abnormally long when not curved to look straight forward during flight. The extra vertebrae help them look straight forward when flying in a horizontal position, easing the stress on their neck, spine, and other muscles whilst flying.

Small plumage feathers run up along the back of the neck, in most species it mixes together with the hair feathering and crest.

 

 

** [3.2] Torso / Abdomen **

[3.2.0] Description

Flighteds have a large barrel-shaped chest, they also have a sternal keel-shaped like an upside-down Y. The keel and collarbone are completely separated to allow more room for muscles. The keel is necessary as the pectoral and wing muscles attach to it, providing extra support for the downward strokes of the wings. The keel forces the chest to protrude slightly, giving their top half a very circular shape.

The pectoral muscles are extremely large as they’re needed to be able to support the wings and to pull them down. This is why they have a further, smaller, second set of pectoral muscles beneath the main ones. These cover most of the chest area.

The pectorals are necessary for pulling the wings down and forward, creating the powerful thrust needed for flight. Their shoulders are broader, and they have a significant amount of upper body strength. Abdominal muscles are clear and defined in both genders. Their back muscles are very strong and thick, but this does not mean they’re inflexible. The lower back muscles are strong enough to support and twist the legs in flight.

 

[3.2.1] Other features

There are many different proportions of muscles between genders. Generally, the larger the wings the larger the proportion of the muscles are, the larger gender in a lot of avians is the female. These larger more extended muscles are the only things that could be considered ‘breasts’ since avians do not have mammary glands.

Avians do not have any nipple-like structures on their chest.

** [3.3] Arms **

[3.3.0] Size

A shortened humerus of the arm means that the upper part of the arm is very compact but noticeably short. The humerus is one of the three bones of the arm. It joins with the scapula at the shoulder joint and with the other bones of the arm, the ulna and radius at the elbow joint. The ulna and radius bone are almost double the length of their humerus, meaning they closely resemble the length of their legs, making a quadrupedal stance easier. The elbow is the hinge joint between the end of the humerus and the ends of the radius and ulna. Even though the humerus is small, it’s compactness means it cannot be broken easily. Its strength allows it to handle loads up to 220 pounds (99kg). The strength of the arm compared to their wings is a lot less.

The wings on avians are the primary limbs on the body. The arms, unfortunately, take second place. The bicep, tricep, and muscles of the forearm are all slightly underdeveloped and noticeably weaker than that of a non-flighted species. This also causes the arms to look thinner than would normal for relative size. The wrist, shoulder, and elbow joint and extremely flexible and reinforced. Able to take the force of walking on them.

 

[3.3.1] Shape

In the avian anatomy, the arm is the part of the upper limb between the glenohumeral joint (shoulder joint) and the elbow joint. In common usage, the arm extends to the hand. It can be divided into the upper arm, which extends from the shoulder to the elbow, the forearm which extends from the elbow to the hand, and the hand. Anatomically the shoulder girdle with bones and corresponding muscles is by definition a part of the arm.

 

[3.3.2] Digits

A hand is a prehensile, multi-fingered organ located at the end of the forearm or forelimb of avians and a few separate mammalian primates.

The avian hand normally has three long digits: two fingers plus one thumb. An average avian hand contains 12 bones, not including the sesamoid bone, the number of which varies between avians. 8 of these bones are phalanges (proximal, intermediate, and distal) of the two fingers and thumb. Phalanges are digital bones in the hands of avians. The metacarpal bones connect the fingers and the carpal bones of the wrist. Each avian hand has four metacarpals, two of which grow into the first finger on the hand, not creating a separate finger, this allows more area on the palm and a place muscles can anchor to, though it’s widely accepted that it used to be a fourth finger that found use elsewhere and is the only reason it survived. They also have five carpal bones.

The wrist of avians fold sideways and outwards very slightly, some avians more than others, hinting to the species therapod ancestry.

Fingers contain some of the densest areas of nerve endings in the body and are the richest source of tactile feedback. They also have the greatest positioning capability of the body; thus, the sense of touch is intimately associated with hands. Like other paired organs (eyes, feet, legs) each hand is dominantly controlled by the opposing brain hemisphere, so that handedness - the preferred hand choice for single-handed activities such as writing with a pencil, reflects individual brain functioning. Around 47% of the avian population is left-handed with 33% being right handed and the rest being ambidextrous.

 

[3.3.3] Claws

They have basic curved claws that are used to help climbing or to hold items in the air.

However, every single avian species has two ‘preening bones’. These are hard, relatively flat, and normally blunted, keratin spikes that can be retracted from the inside base of the thumb and the outside base of the index finger. When pressed together and worked over feathers it cleans and reorders feathers.

Avians have a base-6 numeral system also known as a ‘senary’ numeral system.

 

 

** [3.4] Legs **

[3.4.0] Description

Avians have digitigrade legs meaning they have relatively long carpals and tarsals, and the bones which would correspond to the ankle are thus set much higher in the limb. In avians, this effectively lengthens the foot. Avians walk on their distal and intermediate phalanges. The joint lengths are different for each species, however. Naturally bent digitigrade legs also shift their weight distribution. Both are to offset the massive weight of their wings. The legs are normally left rather loosely bent; their natural posture. But when temporarily straightened to look more threatening or to reach higher it can add whole inches to their height.

They have extra strength in the ankles, knees, and hips. This strength is needed to support themselves and offsets stress when they land from flight, the momentum and hard landing that they must do every time due to their large size would shatter any other animal’s legs. The closest comparison they have to their legs is that of small carnivorous dinosaurs, the kind that they evolved from so it’s not surprising.

The foot, leg and the talons can vary greatly in colour and shade. Anywhere from grey to a lighter or darker shade of their skin tone. Some have unusually coloured legs such as blue-footed booby’s, whose legs are blue. They have feathers that run down the front of the legs, down to the knees in most avians but can grow further down or up depending on the species. These are designed to flow air away from the legs to reduce drag in flight.

 

[3.4.2] Digits

The three-outer specialised curved talons on the end of the feet are used to help support them and balance and grip onto branches and other landing areas, so they don’t fall. It helps stabilise them when they land and keep a grip on even slippery ground when running for take-off. Each of the toes can be webbed in certain species. Talons are stilled called talons whether they’re sharp, blunt, webbed and anything else.

They also have a thumb-like digit placed inside of the foot and slightly away from the rest of the digits. It’s placed like a thumb and acts like one. Without the thumb-digit avians would find gripping branches and balancing more difficult if not impossible. The talons and thumb-digit together are prehensile and can be used to pick up and manipulate items, acting as extra hands.

A dewclaw is a digit on the foot of avians and even the flightless. It grows high on the inside of leg such that when the avian is standing upright, it does not make contact with the ground. It wraps around the back of whatever they’re standing on to balance them though this only applies to things they can wrap their around on (not flat land instead. Only branches or poles).

The position of the claws can also vary, some like humming-avians have them placed very close together for better balance and grip on elevated areas but this can be a drawback on flat land. One or two species even have the outermost claw facing backwards or outwards instead of forwards.

 

[3.4.3] Claws

A talon is the claw of an avian whether it’s sharp or not. The talons are very important; without them, the stability of an avian would be greatly compromised, their ability to run, land, and grip correctly would also be removed, and their biggest defence would be gone. Avians are fully capable of disembowelling others. Some avians such as owls have incredibly long hooked claws, others like seagulls have blunted and shortened ones. The longest claw in normally the inner one.

However, several species of avians have a claw- or nail-like structure hidden under the feathers at the end of their wing digits, notably ostriches, emus, ducks, geese, and kiwis. These can also be used to attack or to help climb.

When in flight the toes curl up to protect the skin against harsh winds. They can easily grab items from swooping down from above. They’re also flexible enough to reach the top of their head with the end of the foot, albeit sitting down.

 

[3.4.4] Other

While avians are comfortable in a hunched bipedal posture this is only a relatively recent trait. Most avians can quite easily roll into a quadrupedal stance even if it’s for only one or two paces. This is mostly seen when climbing or running at high speeds, the stance is almost always used when climbing in things such as trees. When scared or surprised most will move onto four legs and raise their wings with a hiss. Most avians have a preference, either standing bipedal or quadrupedal, it’s considered along the same lines as handedness. It’s quite normal to see avians in a quadrupedal stance walking alongside ones in a bipedal stance.

 

 

** [3.5] Wings **

[3.5.0] Description

Most avians can fly, which distinguishes them from almost most other vertebrate classes. Flight is the primary means of locomotion for most avian species and is used for searching, travel and for escaping from predators. Avians have various adaptations for flight. The bones in the wing are extremely light so that a flighted avian can fly easier. There is also semoid bone in their wings.

An avians wings are the key to flight. Each wing has a central vane to hit the wind, composed of three limb bones, the humerus, ulna and radius. The hand, or manus, is composed three spines that fused early in an avians evolution (digit II, III and IV or I, II, III depending on the scheme followed), one of two groups of flight feathers responsible for the wing's airfoil shape. The other set of flight feathers, behind the carpal joint on the ulna, are called the secondaries. The remaining feathers on the wing are known as coverts, of which there are three sets.

All avians have a spreader bone. A spreader bone is a tiny little bone that connects the ligaments from the shoulder to the wrist. They also have a patagium. A patagium is the membrane between the wing on a flighted. The patagium is important, the curve in the wing it creates increases the surface area. If the patagium gets damaged it means that it will be impossible for them to fly until it’s healed.

The shape of the wing is important in determining the flight capabilities of an avian. Different shapes correspond to different trade-offs between advantages such as speed, low energy use, and manoeuvrability. Two important parameters are the aspect ratio and wing loading. Aspect ratio is the ratio of wingspan to the mean of its chord. Wing loading is the ratio of weight to wing area. The length of bones, how thin or thick they are and what they’re designed to do all have an impact on shape, flight speed, and loading weight. Smaller wings are usually faster and more agile whilst larger wings are more powerful and are better suited for long-distance travel. About 60 extant avian species are flightless, as were many extinct avians.

Because of the wings weight the more they open them when on the ground the further forward a flighted must lean to maintain balance. The tips of the primaries and sometimes the tailfeathers often end up dragging on the floor, though strong melanin and feathering grow there so the feathering doesn’t break or get damaged from the ground. A group of muscles known as the secondary deltoids and triceps (they sit above the trapezius muscles), connect the humerus, ulna/radius, and manus to the spine. This allows independent movement from the primary deltoids and teres, though stretching will cause the wings to lock and straighten in a downward position to compensate for balance.

 

_ [3.5.0.0] The flightless _

Flightless avians are avians that through evolution lost the ability to fly. There are over 60 extant species including the well-known ratites (ostrich, emu, cassowary, rhea, and kiwi) and penguins. Flightlessness has evolved in many different avians independently. The first flightless avian to arrive in each environment utilized the large flightless herbivore or omnivore niche, forcing the later arrivals to remain smaller. In environments where the flightless are not present, it is possible that there were no niches for them to fill.

Two key differences between flighteds and flightless are the smaller wing bones of the flightless and the absent (or greatly reduced) keel on their breastbone. (The keel anchors muscles needed for wing movement.) Adapting to a cursorial lifestyle causes two inverse morphological changes to occur in the skeleto-muscular system: the pectoral apparatus used to power flight is paedorphically reduced while peramorphosis leads to enlargement of the pelvic girdle for running. Repeated selection for cursorial traits across ratites suggests these adaptions comprise a more efficient use of energy in adulthood. The name ‘ratite’ refers to their flat sternum that is distinct from the typical sternum of flighteds because it lacks the keel. This structure is the place where flight muscles attach and thus allow for powered flight.

Flight is the costliest type of locomotion exemplified in the natural world. The energy expenditure required for flight increases proportionally with body size, which is often why flightlessness coincides with body mass. By reducing large pectoral muscles that require a significant amount of overall metabolic energy, ratites decrease their basal metabolic rate and conserve energy. Flighteds have a different wing and feather structures that make flying easier, while the flightless’ wing structures are well adapted to their environment and activities, such as diving in the ocean.

Although selection pressure for flight was largely absent, the wing structure has not been lost except in the New Zealand moas. Ostriches are the fastest running avians in the world. At high speeds, wings are necessary for balance and serving as a parachute apparatus to help the avian slow down. They can go up to a week without eating and survive only off fat stores. If no continued pressures warrant the energy expenditure to maintain the structures of flight, selection will tend towards these other traits.

 

_ [3.5.0.1] Flighted – The Ocean-men (High aspect ratio – Active soaring wings) _

They have low wing loading and are far longer than they are wide and are used for slower flight. This may take the form of almost hovering (as used by kestrel, tern, and nightjars) or in soaring and gliding flight, particularly the dynamic soaring used by Ocean-men, who take advantage of wind speed variation at different altitudes (wind shear) above ocean waves to provide lift.

The open spaces allow for long wings to create good lift with little energy expenditure. They’re also adapted for high speed and dynamic soaring. However, they are less manoeuvrable than the wide, slotted wings of land soarers. A flighted with this kind of wing can glide easily over large expanses of water and have exploited the sea winds. However, Ocean-men must usually run and take off into the wind to get off the ground.

 

_ [3.5.0.2] Flighted – The Hunters/Pretty Boys (Low aspect ratio – Passive soaring wings) _

These wings are favoured by larger species of inland avians, such as eagles, vultures, pelicans, and storks. The slots at the end of the wings, between the primaries, reduce the induced drag and wingtip vortices by ‘capturing’ the energy in air flowing from the lower to upper wing surface at the tips, whilst the shorter size of the wings aids in take-off.

These wings are broad and only relatively long, allowing for take-off and landing in fairly confined areas, high lift, low speed soaring, and slow descents. Many of these flighteds are land soarers with good manoeuvrability required for soaring in the air currents over land and flying through thick brush or forestry.

 

_ [3.5.0.3] Flighted – The Racers (High-speed wings) _

High-speed wings are short, pointed wings that when combined with a heavy wing loading and rapid wingbeats provide an energetically expensive high speed. They can reach high speeds quickly but can also maintain relatively fast speeds over large distances. It also allows them excellent manoeuvrability.

This type of flight is used by the species with the fastest wing speed, the peregrine falcon, as well as by most of the ducks. The same wing shape is used by the auks for a different purpose; auks use their wings to "fly" underwater. The peregrine falcon has the highest recorded dive speed of 242 mph (389 km/h). The fastest straight, powered flight is the spine-tailed swift at 105 mph (170 km/h).

 

_ [3.5.0.4] Flighted – The Ovals (Elliptical wings) _

Elliptical wings are short and rounded, having a low aspect ratio, allowing for tight manoeuvring in confined spaces such as might be found in dense vegetation. As such they are common in forest raptors (such as Accipiter hawks), and many passerines. They are also common in species that use a rapid take off to evade predators, such as pheasants and partridges.

They’re mainly designed for high speeds in short intervals, allowing the flighted to take off quickly and perform a number of acrobatic manoeuvres mid-air. They have an incredibly large alula which forms a mid-wing slot, and several outer primary feathers forming tip slots that provide extra lift.

 

_ [3.5.1] Other Features _

The wing sometimes has vestigial claws. In most species, these are lost by the time the avian is adult, such as the highly visible ones, but claws are retained into adulthood by the secretary avian, screamers, finfoots, ostriches, several swifts and numerous others, as a local trait, in a few specimens.

Ocean-men, or soaring avians, have a locking mechanism in the wing joints that reduce the strain on the muscles during soaring flight.

Avians who have claws on the wrist of their wings often use their wings to aid in quadrupedal walking. Some avians use them over their arms when quadrupedally walking. Other Avians who don’t have these claws still sometimes use them to stabilise themselves on four legs. Sometimes this requires strengthening of the wings in that particular posture.

 

 

** [3.6] Tailfeathers **

[3.6.0] Description

They have much longer and extended pygostyle/tailbone for their tailfeathers. Relative to their weight, height, and size their tailbone is much longer than that it should be. The tailfeathers themselves are much larger than it should be in relative size. They have a single muscle that runs along the back that supports the tail feathers and controls their entire range of movement.

Most avian’s tails end in long feathers called rectrices. The rectrices or tail flight feathers are mainly concerned with stability and control. It also helps the avian to balance when they’re standing or perching above the ground.

They’re used as a rudder, can help to steer, balance, twist, and turn an avian in flight. They also act as a brake for landing. The extra-stiff tail feathers of some avian species allow them to brace themselves firmly upon landing, this is mostly seen in larger avian species’ however. It can also be used to create lift and control drag during slower flights, furling their tails reduces drag during faster flights.

 

[3.6.1] Other features

Avian tails can stand in for vocalisation and speech, too. The most dynamic example is probably Wilson's snipes. During courtship, their tail feathers whir and whistle as they engage in dizzying dances.

In many species of avians, tail feathers have distinct markings that serve no obvious purpose in aviation. That's because many male avians fan their tales and strut during the spring to impress. With stunning plumage topped with eye-like designs, the flagship avian in this category is obviously the peacock. Regardless, many other avian species display similar behaviours. Avians may also use tail feathers to identify their coterie in flocks throughout the year.


	5. [4] Skin / Flesh

** [4] Skin / Flesh **

** [4.0] Type **

The skin has mesodermal cells, pigmentation, such as melanin provided by melanocytes, which absorb some of the potentially dangerous ultraviolet radiation (UV) in sunlight. It also contains DNA repair enzymes that help reverse UV damage. Avian skin pigmentation varies among populations in a striking manner. This has led to the classification of avians on the basis of skin colour and species in the past and still present day in some places.

Because it interfaces with the environment, skin plays an important immunity role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue. This is often discoloured and depigmented.

The epidermis of avians is very similar to that of mammals, with a layer of dead keratin-filled cells at the surface, to help reduce water loss. Hair is a distinctive feature of mammalian skin, while feathers are (at least among living species) similarly unique to avians.

The scales of avians are composed of the same keratin as talons, declaws, and preening bones. They are found mainly on the toes and metatarsus but may be found further up on the ankle in some avians. Most scales do not overlap significantly, except in certain avian species.

The skin is the largest organ in the avian body. The thickness of the skin varies considerably over all parts of the body, and between men and women and the young and the old.  Avians have relatively few skin glands, although there are a few structures for specific purposes, such as the uropygial glands.

Unlike mammals, avians have no hair on their body.

 

 

** [4.1] Colouration **

Avian skin colour ranges in variety from the darkest brown to the lightest hues. An individual's skin pigmentation is the result of genetics, being the product of both of the individual's biological parents' genetic makeup. In evolution, skin pigmentation in avians evolved by a process of natural selection primarily to regulate the amount of ultraviolet radiation penetrating the skin, controlling its biochemical effects.

The actual skin colour of different avians is affected by many substances, although the single most important substance is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin colour of darker-skinned avians. The skin colour of avians with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the haemoglobin circulating in the veins of the dermis. Colour is not entirely uniform across an individual's skin; for example, the skin of the palm, the sole of the foot, and any skin covered by feathers are lighter than most other skin, and this is especially noticeable in darker-skinned avians.

There is a direct correlation between the geographic distribution of ultraviolet radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that receive higher amounts of UVR generally located closer to the equator, tend to have darker-skinned populations. Areas that are far from the tropics and closer to the poles have a lower intensity of UVR, which is reflected in lighter-skinned populations.

The social significance of differences in skin colour has varied across cultures and over time, as demonstrated regarding social status and discrimination.


	6. [5] Feathers

**Notes for the Chapter:**

> Finally got to the main feature of a flying being; the freakin feathers.

** [5] Feathers **

** [5.0] Description **

Feathers are epidermal growths that form the distinctive outer covering, or plumage, on avians. They are considered the most complex integumentary structures found in vertebrates and a premier example of a complex evolutionary novelty.

Feathers are a feature characteristic of avians. They facilitate flight, provide insulation that aids in thermoregulation, and are used in display, camouflage, and signalling. There are several types of feathers, each serving its own set of purposes. Feathers are epidermal growths attached to the skin and arise only in specific tracts of skin called pterylae. The distribution pattern of these feather tracts (pterylosis) is used in taxonomy and systematics. The arrangement and appearance of feathers on the body, called plumage, may vary within species by age, social status, and sex.

Feathers require maintenance and avians preen or groom them daily, spending an average of around 11% (2 and half hours) of their daily time on this. The preening bones in the hand are used to brush away foreign particles and to apply waxy secretions from the uropygial gland; these secretions protect the feathers' flexibility and act as an antimicrobial agent, inhibiting the growth of feather-degrading bacteria.

 

 

** [5.1] Classification(s) **

There are two basic types of feather: vaned feathers which cover the exterior of the body, and down feathers which are underneath the vaned feathers. Also called contour feathers, vaned feathers arise from tracts and cover the entire body.

The third type of feather is called a filoplume. Filoplumes are hairlike feathers with a few soft barbs near the tip. These cover the skin areas were growth from other types of feathers are rare.

The remiges, or flight feathers of the wing, and rectrices, the flight feathers of the tail are the most important feathers for flight. A typical vaned feather features a main shaft, called the rachis. Fused to the rachis are a series of branches or barbs; the barbs themselves are also branched and form the barbules. These barbules have minute hooks called barbicels for cross-attachment.

The down of avians is a layer of fine feathers found under the tougher exterior feathers. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap air and provide excellent thermal insulation. Young avians are clad only in natal down until their true feathers grow in.

At the base of the feather, the rachis expands to form the hollow tubular calamus (or quill) which inserts into a follicle in the skin. The basal part of the calamus is without vanes. This part is embedded within the skin follicle and has an opening at the base (proximal umbilicus) and a small opening on the side (distal umbilicus).

Flight feathers are stiffened so as to work against the air in the downstroke but yield in other directions. It has been observed that the orientation pattern of β-keratin fibres in the feathers of flighted differs from that in the flightless: the fibres are better aligned along the shaft axis direction towards the tip, and the lateral walls of rachis region show structure of crossed fibres.

 

 

** [5.2] Function(s) **

Feathers insulate avians from water and cold temperatures. The individual feathers in the wings and tail play important roles in controlling flight. Some species have a crest of feathers on their heads. Although feathers are light, an avian's plumage weighs two or three times more than their skeleton, since many bones are hollow and contain air sacs.

Some avians have a supply of powder down feathers which grow continuously, with small particles regularly breaking off from the ends of the barbules. These particles produce a powder that sifts through the feathers on the avian’s body and acts as a waterproofing agent and a feather conditioner. They may be scattered in plumage or in localized patches on the breast, belly, or flanks. On most avians the feathers can easily become waterlogged, causing the avian to sink, however light to medium rain is rarely a problem.

Of course, they’re also the only reason an avian is able to fly.

 

 

** [5.3] Distribution **

Contour feathers are not uniformly distributed on the skin of the avian except in some groups such as the penguins, ratites, and screamers. In most avians the feathers grow from specific tracts of skin called pterylae; between the pterylae, there are regions which are free of feathers called apterylae (or apteria). Filoplumes and down may arise from the apterylae. The arrangement of these feather tracts, pterylosis or pterylography, varies greatly.

Flight worthy feathers are found only along the wing and tail. Softer feathers can be found in many different areas of the body depending on species. They can be found along the back acting as a mantle, the feathering that visually connects the wings, tailfeathers, and neck together. They also help wind pass more easily and quickly over the back, forcing it down to the tailfeathers so they can fly easier and change directions with less effort. Without them, flight is hard but not impossible.

Plumage feathers can also be found along the head, legs down to the knees, back of the neck, and sometimes over the shoulders and chest. However, a physical mix of plumage feathers and flight feathers; soft but with a hard bard similar to flight feathers can be found along the outside of the forearm (these are used mainly for displays), though some avians or entire avian species have these missing.

 

 

** [5.4] Feather colours **

The colours of feathers are produced by pigments, by microscopic structures that can refract, reflect, or scatter selected wavelengths of light, or by a combination of both.

Most feather pigments are melanin’s (brown and beige pheomelanins, black and grey eumelanins) and carotenoids (red, yellow, orange); other pigments occur only in certain taxa – the yellow to red psittacofulvins and the red turacin and green turacoverdin (porphyrin pigments found only in turacos).

Structural colouration is involved in the production of blue colours, iridescence, most ultraviolet reflectance and in the enhancement of pigmentary colours. White feathers lack pigment and scatter light diffusely; albinism and leucism in avians is caused by defective pigment production, though structural colouration will not be affected.

The blues and bright greens are produced by constructive interference of light reflecting from different layers of structures in feathers. In the case of green plumage, in addition to yellow, the specific feather structure involved is called by some the Dyck texture. Melanin is often involved in the absorption of light; in combination with a yellow pigment, it produces a dull olive-green.

The reds, orange and yellow colours of many feathers are caused by various carotenoids. Carotenoid-based pigments might be honest signals of fitness because they are derived from special diets and hence might be difficult to obtain, and/or because carotenoids are required for immune function and hence sexual displays come at the expense of health.

If there’s a colour you can name be sure that somewhere there’s a flighted or whole species with that colour.

 

 

** [5.5] Abnormal colouring **

[5.5.0] Leucism

Leucism is a condition in which there is partial loss of pigmentation in an avian resulting in white, pale, or patchy colouration of the skin, feathers, scales, talons, but not the eyes. Unlike albinism, it is caused by a reduction in multiple types of pigment, not just melanin.

Leucism is a general term for the phenotype resulting from defects in pigment cell differentiation and/or migration from the neural crest to skin, hair, or feathers during development. This results in either the entire surface (if all pigment cells fail to develop) or patches of body surface (if only a subset are defective) having a lack of cells capable of making pigment.

Since all pigment cell-types differentiate from the same multipotent precursor cell-type, leucism can cause the reduction in all types of pigment. This is in contrast to albinism, for which leucism is often mistaken.

More common than a complete absence of pigment cells is localized or incomplete hypopigmentation, resulting in irregular patches of white on an avian that otherwise has normal colouring and patterning. This partial leucism is known as a ‘pied’ or ‘piebald’ effect, and the ratio of white to normal-coloured skin can vary considerably not only between generations, but between different offspring from the same parents, and even between members of the same nestmates.

A further difference between albinism and leucism is in eye colour. Most leucistic avians have normal coloured eyes. This is because the melanocytes of the RPE are not derived from the neural crest, instead, an outpouching of the neural tube generates the optic cup which, in turn, forms the retina. As these cells are from an independent developmental origin, they are typically unaffected by the genetic cause of leucism.

 

[5.5.1] Albinism

Albinism in avians is a congenital disorder characterized by the complete or partial absence of pigment in the skin, feathers, and eyes. Albinism is associated with a number of vision defects, such as photophobia, nystagmus, and amblyopia. Lack of skin pigmentation makes for more susceptibility to sunburn and skin cancers. In rare cases, albinism may be associated with deficiencies in the transportation of melanin granules. This also affects essential granules present in immune cells leading to increased susceptibility to infection.

Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrates, including avians. It is due to absence or defect of tyrosinase, a copper-containing enzyme involved in the production of melanin. Avians have multiple pigments and for these, albinism is considered to be a hereditary condition characterised by the absence of melanin in particular, in the eyes, skin, scales, feathers, talons, or cuticle.

In avians, there are two principal types of albinism: oculocutaneous, affecting the eyes, skin and feathers, and ocular affecting the eyes only.

There are different types of oculocutaneous albinism depending on which gene has undergone mutation. With some, there is no pigment at all. With ocular albinism, the colour of the iris of the eye may vary from blue to green or even brown and sometimes darkens with age. However, when an eye doctor examines the eye by shining a light from the side of the eye, the light shines back through the iris since very little pigment is present.

Because individuals with albinism have skin that entirely lacks the dark pigment melanin, which helps protect the skin from the sun's ultraviolet radiation, their skin can burn more easily from overexposure.

The avian eye normally produces enough pigment to colour the iris blue, green or brown and lend opacity to the eye. Lack of pigment in the eyes also results in problems with vision, both related and unrelated to photosensitivity.

Those afflicted with albinism are generally as healthy as the rest of the population, with growth and development occurring as normal, and albinism by itself does not cause mortality, although the lack of pigment blocking ultraviolet radiation increases the risk of skin cancers and other problems.

Development of the optical system is highly dependent on the presence of melanin. For this reason, the reduction or absence of this pigment in people with albinism may lead to: Misrouting of the retinogeniculate projections, resulting in abnormal decussation (crossing) of optic nerve fibres Photophobia and decreased visual acuity due to light scattering within the eye. Photophobia is specifically when light enters the eye, unrestricted and with full force. It is painful and causes extreme sensitivity to light. Reduced visual acuity due to foveal hypoplasia and possibly light-induced retinal damage.

Eye conditions common in albinism include: Nystagmus, irregular rapid movement of the eyes back and forth, or in a circular motion. Amblyopia, decrease in acuity of one or both eyes due to poor transmission to the brain, often due to other conditions such as strabismus. Optic nerve hypoplasia, underdevelopment of the optic nerve.

The improper development of the retinal pigment epithelium, which in normal eyes absorbs most of the reflected sunlight, further increases glare due to light scattering within the eye. The resulting sensitivity (photophobia) generally leads to discomfort in bright light, but this can be reduced by the use of sunglasses or brimmed hats.

 

[5.5.2] Melanism

Melanism is a development of the dark-coloured pigment melanin in the skin or its appendages and is the opposite of albinism.

Pseudo-melanism, also called abundism, is another variant of pigmentation, characterized by dark spots or enlarged stripes, which cover a large part of the body of the animal, making it appear melanistic. A deficiency in or total absence of melanin pigments is called amelanism.

The morbid deposition of black matter, often of a malignant character causing pigmented tumours, is called melanosis.

 

 

** [5.6] Dimorphism **

Sexual dimorphism in avians can be manifested in size or plumage differences between the sexes. Sexual size dimorphism varies with females typically being larger, though this is not always the case. Plumage dimorphism, in the form of ornamentation or colouration, also varies, though males are typically the more ornamented or brightly coloured sex. Since females are the prime caregivers, evolution has helped select females to display duller coloured down so that they would blend into their environment. She also has select traits that make her feathers dull and often allow her to blend into the surroundings.

Sexual dimorphism in their feathers only appear during mating season in some avian species, some species of avians only show dimorphic traits in seasonal variation. The males of these species will moult into a less bright or less exaggerated colour during the off-breeding season. This occurs because the species is more focused on survival than reproduction, causing a shift into a less ornate state.

The top and bottom colours may be different, in order to provide camouflage during flight. Striking differences in feather patterns and colours are part of the sexual dimorphism of many avian species and are particularly important in the selection of mating pairs. In some cases, there are differences in the UV reflectivity of feathers across sexes even though no differences in colour are noted in most avians visible range.

Males are almost always the brightly coloured and more ‘unique’ sex.

 

 

** [5.7] Moulting **

In avians, moulting is the periodic replacement of feathers by shedding old feathers while producing new ones. Feathers are dead structures at maturity which are gradually abraded and need to be replaced. Adult avians moult at least once a year, although many moult twice and a few three times each year. It’s generally a slow process as avians rarely shed all their feathers at any one time; the avian must retain sufficient feathers to regulate its body temperature and repel moisture. The number and area of feathers that are shed varies. In some moulting periods, an avian may renew only the feathers on the head and body, shedding the wing and tail feathers during a later moulting period. Some species of avian become flightless during an annual wing moult.

While the plumage may appear thin or uneven during the moult, the avian's general shape is maintained despite the loss of apparently many feathers; bald spots are typically signs of unrelated illnesses, such as gross injuries, parasites, feather pecking, or feather plucking.

The process of moulting in avians is as follows: First, the avian begins to shed some old feathers, then pin feathers grow in to replace the old feathers. As the pin feathers become full feathers, other feathers are shed. This is a cyclical process that occurs in many phases. It is usually symmetrical, with feather loss equal on each side of the body. Because feathers make up 4–12% of an avian's body weight, it takes a large amount of energy to replace them. For this reason, moults often occur immediately after the breeding season. The plumage produced during this time is called postnuptial plumage. Prenuptial moulting occurs where the males replace their nonbreeding plumage with breeding plumage. Large avian species’ can advance the moult of severely damaged feathers.

 

 

** [5.8] Uropygial gland **

The uropygial gland, informally known as the preen gland or the oil gland, is a bilobate sebaceous gland possessed by the majority of avians. It is located dorsally at the base of the tail (between the fourth caudal vertebrae and the pygostyle) and is greatly variable in both shape and size. In some species, the opening of the gland has a small tuft of feathers to provide a wick for the preen oil. It is a holocrine gland enclosed in a connective tissue capsule made up of glandular acini that deposit their oil secretion into a common collector tube ending in a variable number of pores (openings), most usually two. Each lobe has a central cavity that collects the secretion from tubules arranged radially around the cavity. The gland secretion is conveyed to the surface via ducts that, in most species, open at the top of a papilla (nipple-like structure).

The uropygial gland secretes an oil (preen oil) through the dorsal surface of the skin via a grease nipple-like nub or papilla. The oil contains a complex and variable mixture of substances formed greatly of aliphatic monoester waxes, formed of fatty acids and monohydroxy wax-alcohols.

An avian will typically transfer preen oil to their feathers during preening by rubbing their fingers and/or preening bones against the gland opening and then rubbing the accumulated oil on the feathers of the body and wings, and on the skin of the feet and legs.

The preen oil helps maintain the integrity of the feather structure. In Ocean-men, the oil maintains the flexibility of feathers and keeps feather barbules from breaking. The interlocking barbules, when in good condition, form a barrier that helps repel water. In some species, preen oil also maintains the integrity of the scaly skin of the legs and feet.

 

 

** [5.9] Preening **

Preening is good for many things:

Moisturizing feathers with preen oil so they are flexible and strong, instead of brittle and easily breakable. This helps feathers better withstand the stress of flight. Aligning feathers for optimum waterproofing and insulation to protect against adverse conditions, such as soaking or extremely hot or cold temperatures. Aligning feathers into the most aerodynamic shape for easier, more efficient flight. This helps avians use less energy in flight and make more acrobatic moves.

Removing feather parasites and body lice that can destroy feathers or carry disease. This keeps avians healthier and protects the entire family from an outbreak. Removing tough sheaths from newly moulted feathers. Removing these sheaths helps gets feathers into the proper position more quickly so they can be useful right away. Creating a healthier appearance to attract a mate. A healthier, more attractive avian will attract a stronger mate and have a better chance of raising many strong chicks.

Bonding between mates as a courtship ritual that involves mutual preening, called allopreening. This is a form of communication between mates and helps keep their connection strong.

 

 

** [5.10] Other Features **

Feathers being critical to the survival of an avian, require maintenance. Apart from physical wear and tear, feathers face the onslaught of fungi, ectoparasitic feather mites and avianlice. The physical condition of feathers is maintained by preening often with the application of secretions from the preen gland.

Many avians will take dust baths as part of their regular preening. The dust helps dislodge parasites and absorbs excess preen oil, so feathers are not too heavily coated. Avians that do not bathe in water are more likely to use dust baths frequently, but many avians will use both types of bathing.

Many avians will bathe in water before engaging in extensive preening, splashing around to moisten all their feathers. Bathing removes dust, dirt, and parasites from feathers before avians work to put each feather into its proper position. While some avians dip into shallow water others, mainly the Ocean-men, prefer to fully submerge themselves. Avians in arid regions make use of loose soil to dust-bathe.

Sunning helps avians control body parasites and feather mites by moving these pests around to different areas of the body where they can be easily combed away. Sunning can also make the oil from the preen glad more liquid and easier to spread to different feathers in a thin, even layer.

Extensive stretching helps provide space between each feather, so the entire feather can be stroked and groomed effectively. Stretching or fluffing also helps avians align all their feathers after a section has been preened.

**Notes for the Chapter:**

> The next chapters about sex ;)


	7. [6] Genitals / Sexual organs

**Notes for the Chapter:**

> !!! This is where we now talk about the private parts of avians. I’m not squeamish about these things but I understand that some people are. This is mainly descriptions of each genders privates in a purely scientific manner. The actual sexual act is very briefly touched upon. Feel free to skip this part if you need.

** [6] Genitals / Sexual organs **

** [6.0] Male / Cock Genitals **

The penis is the male (or cock’s) intromittent organ placed in the pelvic region. An avian penis is expectantly different in structure from mammal penises, being erected by lymph, not blood. It is usually partially feathered and in some species, features spines and brush-like filaments. The penis remains stored internally when it is not erect. When the male becomes sexually aroused, the penis becomes erect and ready for sexual activity. Erection occurs because sinuses within the erectile tissue of the penis become filled with lymph.

The male genital system is immature at birth and develops to maturity at puberty. Male avians do not experience breeding season arousal until they’re mature.

Male avians have two descended testicles that rest on the ventral body wall. Their testes will become enlarged during the breeding season to produce sperm, outside of this time they normally remain empty with no or little sperm. (Arousal is uncommon, Sex is hard to accomplish, and reproduction is impossible outside of the avians breeding season.) The testes in avians are generally asymmetric with most avians having a larger left testis.

Sex is mainly getting both partners aroused enough for the male to ejaculate. Copulation occurs through brief insertion of the male organ into the vagina before ejaculation.

 

 

** [6.1] Female / Hen Genitals **

The female (or hen) genital system is made up of the internal and external sex organs that function in avian reproduction. The female genital system is immature at birth and develops to maturity at puberty to be able to produce gametes and experience breeding season arousal. The internal sex organs are the uterus and Fallopian tubes, and the ovaries.

The vagina is a fibromuscular canal leading from the outside of the body to the cervix of the uterus or womb. It is also referred to as the birth canal in the context of pregnancy. The vagina accommodates the male penis during sexual intercourse. Semen containing spermatozoa is ejaculated from the male into the vagina potentially enabling fertilization of the ovum to take place.

The cervix is the neck of the uterus, the lower, narrow portion where it joins with the upper part of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall. Approximately half its length is visible, the remainder lies above the vagina beyond view.

The uterus or womb is the major female reproductive organ. The uterus provides mechanical protection, nutritional support. The uterus contains three suspensory ligaments that help stabilize the position of the uterus and limits its range of movement. The uterosacral ligaments keep the body from moving inferiorly and anteriorly. The round ligaments restrict posterior movement of the uterus. The cardinal ligaments also prevent the inferior movement of the uterus. The uterus is a pear-shaped muscular organ. Its major function is to accept a fertilized ovum which becomes implanted into the endometrium and derives nourishment from blood vessels which develop exclusively for this purpose. The fertilized ovum becomes an embryo, develops into a foetus, and gestates until birth.

The Fallopian tubes are two tubes leading from the ovaries into the uterus. On maturity of an ovum, the follicle and the ovary's wall rupture, allowing the ovum to escape and enter the Fallopian tube. There it travels toward the uterus, pushed along by movements of cilia on the inner lining of the tubes.

The ovaries are small, paired organs located near the lateral walls of the pelvic cavity. These organs are responsible for the production of the ova and the secretion of hormones. The process by which the ovum is released is called ovulation.

 

**Notes for the Chapter:**

> If you want to know how I acquired and researched all this information, I’ll just tell you my internet history is now in utter shambles.


	8. [7] Internals

** [7] Internals **

** [7.0] Dentition **

Avians, unlike their closest relatives, reptiles, have heterodont teeth. This where teeth are differentiated into different forms such as incisors, canines, premolars, and molars. The teeth also have deep roots. They’re also a polyphyodonty, where their teeth are continually replaced. New, permanent teeth grow in the jaws, usually under or just behind the old tooth, from stem cells in the dental lamina. Chicks typically have a full set of teeth when they’re born; there is no tooth change before birth. Within days, tooth replacement begins, usually in the back of the jaw continuing forward like a wave. On average a tooth is replaced every two months. Overall, avians may use over 7,000 teeth from birth to death.

Avians usually have 20 teeth at birth. As they age fledgelings will grow new teeth alongside the rest. Most avians, by the time they’re adults, have 32 teeth, these will be lost and regrown regularly like their younger teeth. Damage to the teeth is painful but rarely ever permanent, as any damage done will be removed when it regrows. Because of this avians can put a lot more pressure into bites even at the risk of damage to the teeth. The teeth of an avian are classified as incisors, canines, premolars, and carnassials.

 

Incisors are the front teeth of avians. They’re located in the premaxilla above and on the mandible below. Avians have a total of four (two on top and bottom). Incisors are sharp (but not as long or sharp as the canines) and are shaped like points, they’re mainly used for tearing, slicing, and grasping food.

Avians have four canine teeth: two in the upper and two in the lower arch. A canine is placed laterally to each lateral incisor. They are larger and stronger than the incisors, they’re curved forward and end with a sharp point for stabbing and impaling. They’re often called fangs. In avians, the upper canine teeth are larger and longer than the lower and usually, present a distinct basal ridge. The lower canine teeth are placed nearer the middle line than the upper so that their summits correspond to the intervals between the upper canines and the lateral incisors.

The premolar teeth are transitional teeth located between the canine and carnassials. Avians have twelve premolars total in the mouth (three on top and bottom). Premolars can be considered as 'transitional teeth' during chewing. They have properties of both the anterior canines and carnassials, and so food can be transferred from the canines to the premolars and finally to the carnassials for grinding, instead of directly from the canines to the carnassials.

Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. Avians have 12 of these (six on the top six on the bottom) just like their premolars and are placed at the back of the mouth. The jaw of an avian is strong enough to use their carnassials to inflict damage or even a killing blow, by either crushing the windpipe or slicing the spine. An avians carnassial teeth benefit from most of the force generated by the mastication muscle, allowing for efficient shearing, and cutting of flesh, tendon, and muscle, though with enough force they can also grind away bone.

 

 

** [7.1] Saliva **

Avian saliva comprises 98% water, plus electrolytes, mucus, white blood cells, epithelial cells, glycoproteins, antimicrobial agents such as lysozyme. saliva serves a lubricative function, wetting food and permitting the initiation of swallowing and protecting the mucosal surfaces of the oral cavity from desiccation.

Estimates range that around 0.75 to 1.5 litres of saliva is produced by an avian per day. During sleep, the amount drops to nearly zero. In avians, the submandibular gland contributes around 70–75% of secretion, while the parotid gland secretes about 20–25% and small amounts are secreted from the other salivary glands.

Saliva maintains the pH of the mouth. Saliva is supersaturated with various ions. Certain salivary proteins prevent precipitation, which would form salts. These ions act as a buffer, keeping the acidity of the mouth within a certain range, typically pH 7.5 to 8.7. This prevents minerals in the dental hard tissues from dissolving. Avian saliva also has antibacterial properties. This is why an avians first reaction to a wound will be to lick it, which can sometimes help to promote healing.

 

 

** [7.2] Digestive system **

[7.2.0] Higher digestive systems

Most avians are carnivorous and have rather simple and comparatively short digestive tracts, meat being fairly simple to break down and digest. Digestion, however, is slower than that found in most mammals. Herbivorous avians face the same problems.

Food enters the mouth where it’s chewed. The tongue is a fleshy and muscular sensory organ, and the very first sensory information is received via the taste buds in the papillae on its surface. If the taste is agreeable, once the food has been chewed and softened they will swallow it down through the oesophagus.

The oesophagus, commonly known as the gullet, is an organ which consists of a muscular tube through which food passes from the pharynx to the stomach. It passes through the posterior mediastinum in the thorax and enters the stomach through a hole in the thoracic diaphragm – the oesophageal hiatus.

 

[7.2.1] Stomach

The stomach is a major organ and the largest part of the gastrointestinal tract and digestive system. It’s also the first part of the body to further digestion as avians have no enzymes inside their saliva. The gastric acid produced in the stomach plays a vital role in the digestive process, the acid in their stomach operates between pH 1 and pH 2. The stomach also secretes powerful digestive enzymes with about 10 times the amount of hydrochloric acid compared to other species. Most enzymes are extremely sensitive to pH and won’t function in the wrong environment. If an avian eats inappropriate food, then their digestive system can’t function properly. Mucus is secreted by innumerable gastric glands in the stomach, to provide a slimy protective layer against the damaging effects of the chemicals.

Avians can consume up to 5% of their body weight in an extremely short period. The inside of an avian’s stomach contains a large number of folds. It expands when full and its muscles massage the food to ensure that the digestive juices work properly. Once all the digestible pieces of food have been dissolved, the muscles squeeze the now liquid mass into the intestine for the final stage of the process and for the absorption of the nutrients. An avian’s stomach is designed to finish digesting one meal before being filled again.

(Avians are carnivores. True, they can and do eat vegetable matter, but anatomically they are designed to catch, kill, and eat prey (or meat, raw or cooked, in modern day). Large amounts of plant matter can make an avian sick though. Fully herbivorous avians are considered outliers.)

 

[7.2.2] Lower digestive systems

The spleen breaks down both red and white blood cells that are spent. A product of this digestion is the pigment bilirubin, which is sent to the liver and secreted in the bile. Another product is iron, which is used in the formation of new blood cells in the bone marrow.

The liver is the third largest organ and is an accessory digestive gland which plays a role in the body's metabolism. The liver has many functions some of which are important to digestion. The liver can detoxify various metabolites; synthesise proteins and produce biochemicals needed for digestion. It regulates the storage of glycogen which it can form from glucose. The liver can also synthesise glucose from certain amino acids. Its digestive functions are largely involved in the breaking down of carbohydrates. Fats are also produced in the process of lipogenesis. The liver synthesises the bulk of lipoproteins. The liver produces bile, an important alkaline compound which aids digestion.

The pancreas is a major organ functioning as an accessory digestive gland in the digestive system. It is both an endocrine gland and an exocrine gland. The endocrine part secretes insulin when the blood sugar becomes high; insulin moves glucose from the blood into the muscles and other tissues for use as energy. The endocrine part releases glucagon when the blood sugar is low; glucagon allows stored sugar to be broken down into glucose by the liver in order to re-balance the sugar levels. The pancreas produces and releases important digestive enzymes in the pancreatic juice that it delivers to the duodenum. Aqueous pancreatic secretions from pancreatic duct cells contain bicarbonate ions which are alkaline and help with the bile to neutralise the acidic chyme that is churned out by the stomach. The pancreas is also the main source of enzymes for the digestion of fats and proteins.

 

[7.2.3] Intestinal tracts

_ [7.2.3.0] Small intestine _

The small intestines of an avian are relatively short at around four times an avians body length, as avians are a carnivorous species. Food starts to arrive in the small intestine around two hours after it is eaten, and after four hours the stomach has emptied. Until this time the food is termed a bolus. It then becomes the partially digested semi-liquid termed chyme. Most food digestion takes place in the small intestine.

In the small intestine, the pH becomes crucial; it needs to be finely balanced in order to activate digestive enzymes. The chyme is very acidic, with a low pH, having been released from the stomach and needs to be made much more alkaline. The chyme arrives in the intestines having been released from the stomach through the opening of the pyloric sphincter. The resulting alkaline fluid mix neutralises the gastric acid which would damage the lining of the intestine. The mucus component lubricates the walls of the intestine.

Food continues to travel along the small intestine by peristalsis. The small intestine can be divided into the duodenum, jejunum, and the ileum. The pancreatic duct connects the pancreas to the duodenum – the majority of the digestive enzymes enter the small intestine by this duct. To aid inlipid digestion, bile is secreted by the liver (stored in the gallbladder). Bile emulsifies lipids which give them a larger surface area, increasing enzyme efficiency.

When the digested food particles are reduced enough in size and composition, they can be absorbed by the intestinal wall and carried to the bloodstream. Circular folds inside the jejunum also slow the passage of food giving more time for nutrients to be absorbed. When the chyme is exhausted of its nutrients the remaining waste material changes into the semi-solids called faeces, which pass to the large intestine.

 

_ [7.2.3.1] Caecum _

The caecum of an avian is mostly vestigial and holds very little purpose in digesting meat items. However, in more herbivorous avians it can become useful as for them it’s used as a site of bacterial fermentation of plant matter.

 

_ [7.2.3.2] Large intestine _

The large intestine absorbs minimal nutrients from the ingested food; instead, its primary role is the reabsorption of water, vitamins, and electrolytes from the mixture of food, saliva and gastric & pancreatic juices passing through. This prevents excessive water loss and therefore dehydration. The remnants are excreted via the rectum and anal sphincters.

 

_ [7.2.3.3] Regurgitation _

Unlike mammals, many avians do not excrete the bulky portions (roughage) of their undigested food such feathers, fur, bone fragments, and seed husks. Most regurgitate them as food pellets. Whilst this was common in more prehistoric times, with modern food being mostly pre-prepared the regurgitation of pellets is rarely needed.

 

 

** [7.3] Respiratory system **

The respiratory system of avians differs significantly from that found in mammals. They have an extensive system of air sacs distributed throughout their bodies. In avians, the lungs expand very little because the air goes through them into the air sacs and back through the lungs on expiration. Thus, not only can a greater volume of air pass through the lungs, but since it passes through twice, gas exchange is more efficient. In addition, avians’ lungs have more capillaries/area than mammals. Avian lungs are smaller than those in mammals of comparable size, but the air sacs account for 15% of the total body volume.

Avians have one of the most complex respiratory systems of all animal groups. Upon inhalation, 75% of the fresh air bypasses the lungs and flows directly into a posterior air sac which extends from the lungs and connects with air spaces in the bones and fills them with air. The other 25% of the air goes directly into the lungs. When the avian exhales, the used air flows out of the lungs and the stored fresh air from the posterior air sac is simultaneously forced into the lungs. Thus, an avian's lungs receive a constant supply of fresh air during both inhalation and exhalation.

The trachea is an area of dead space: the oxygen-poor air it contains at the end of exhalation is the first air to re-enter the posterior air sacs and lungs. In comparison to the mammalian respiratory tract, the dead space volume in an avian is, on average, 4.5 times greater than it is in mammals of the same size. Avians with their long necks inevitably have longer tracheae, and must, therefore, take deeper breaths than mammals do to make allowances for their greater dead space volumes.

The exhaled air also draws the heat from the avians body out. Without this removing a large amount of heat from the body avians would burn themselves up from the inside out.

 

 

** [7.4] Circulatory system **

Most avians are endothermic homeotherms, meaning that primarily produce their own heat and that have a constant body temperature. However, some are endothermic poikilotherms means that their body temperature adjusts depending on the environment.

The avian circulatory system is driven by a four-chambered, myogenic heart contained in a fibrous pericardial sac. This pericardial sac is filled with a serous fluid for lubrication. The heart itself is divided into a right and left half, each with an atrium and ventricle. The atrium and ventricles of each side are separated by atrioventricular valves which prevent backflow from one chamber to the next during contraction.

The sinoatrial node uses calcium to cause a depolarising signal transduction pathway from the atrium through right and left atrioventricular bundle which communicates contraction to the ventricles. The avian heart also consists of muscular arches that are made up of thick bundles of muscular layers. Much like a mammalian heart, an avian heart is composed of endocardial, myocardial and epicardial layers. The atrium walls tend to be thinner than the ventricle walls, due to the intense ventricular contraction used to pump oxygenated blood throughout the body. Avian hearts are generally larger than mammalian hearts when compared to body mass. This adaptation allows more blood to be pumped to meet the high metabolic need associated with flight.

Avians have a very efficient system for diffusing oxygen into the blood; avians have a ten times greater surface area to gas exchange volume than mammals. As a result, avians have more blood in their capillaries per unit of volume of the lung than a mammal. The arteries are composed of thick elastic muscles to withstand the pressure of the ventricular constriction and become more rigid as they move away from the heart. Blood moves through the arteries, which undergo vasoconstriction, and into arterioles which act as a transportation system to distribute primarily oxygen as well as nutrients to all tissues of the body. As the arterioles move away from the heart and into individual organs and tissues they are further divided to increase the surface area and slow blood flow. Blood travels through the arterioles and moves into the capillaries where gas exchange can occur.

Capillaries are organized into capillary beds in tissues; it is here that blood exchanges oxygen for carbon dioxide waste. In the capillary beds, blood flow is slowed to allow maximum diffusion of oxygen into the tissues. Once the blood has become deoxygenated it travels through venules then veins and back to the heart. Veins, unlike arteries, are thin and rigid as they do not need to withstand extreme pressure. As blood travels through the venules to the veins a funnelling occurs called vasodilation bringing blood back to the heart. Once the blood reaches the heart it moves first into the right atrium, then the right ventricle to be pumped through the lungs for further gas exchange of carbon dioxide waste for oxygen. Oxygenated blood then flows from the lungs through the left atrium to the left ventricle where it is pumped out to the body.

Normal avian body temperature, also known as normothermia or euthermia, is the typical temperature range found in avians. The normal avian body temperature range is typically around 40.3–42.6 °C. This is due to a much higher metabolism and activity level. The high metabolism of avians requires rapid circulation of the blood because waste products build up quickly in the cells and must be removed before they reach a toxic level.

 

 

** [7.5] Nervous system **

The nervous system of an avian consist of the brain, sense organs, and nerves. Nerves carry messages from sense organs, such as the eyes, to the brain. Nerves also carry messages from the brain to the muscles.

As a group, avians have the best vision of all animals. Large eyes provide keen sight and excellent colour perception. Avians that are most active at night, or nocturnal, also have well-developed sight. The range of vision depends on how far apart their eyes are placed on their head.

Hearing is also well developed in avians, with some nocturnal avians having especially acute hearing. Only a few avians, such as the kiwi, have a highly developed sense of smell.

 

 

** [7.6] Skeletal system **

The avian skeleton is highly adapted for flight. It is extremely lightweight but strong enough to withstand the stresses of taking off, flying, and landing. One key adaptation is the fusing of bones into single ossifications. Because of this, avians usually have a smaller number of bones than other terrestrial vertebrates.

Avians have many bones that are pneumatized, meaning they have crisscrossing struts, or trusses, across the inside of the bone designed for strength and support. They’re also denser which makes them more durable against strain and breakages. The number of pneumatized bones varies among species, though large gliding and soaring avians tend to have the most. Respiratory air sacs often form air pockets within the semi-hollow bones of the avian's skeleton.

The bones of avians designed for diving are often less hollow than those of non-diving species. Penguins, loons, and puffins are without pneumatized bones entirely. The flightless, such as ostriches and emus, demonstrate osseous pneumaticity, possessing pneumatized femurs and, in the case of the emu, pneumatized cervical vertebrae.

Avians also have more cervical (neck) vertebrae than many other animals; most have a highly flexible neck consisting of many vertebrae, this allows them to look directly forward whilst in flight.

Avians are the only vertebrates to have fused clavicles (collarbone) (the furcula or wishbone) or a keeled sternum or breastbone. The keel of the sternum serves as an attachment site for the muscles used for flight or, similarly, for swimming, in penguins. Again, the flightless, such as ostriches, which do not have highly developed pectoral muscles, lack a pronounced keel on the sternum. Swimming avians have a wide sternum while walking avians have a long or high sternum and the flighted have an extremely large keel.

Avians have uncinate processes on the ribs. These are hooked extensions of bone which help to strengthen the rib cage by overlapping with the rib behind them. This feature is also found in the tuatara. They also have a slightly elongated tetradiate pelvis, similar to some reptiles. The hind limb has an intra-tarsal joint found also in some reptiles. There is extensive fusion of the trunk vertebrae as well as fusion with the pectoral girdle. The ribcage and pelvis are placed closer together, which means that the body is less flexible at the waist compared to the flightless. However, this means that less energy is spent trying to keep the pelvis up. A flighted also has a lengthened pelvis that provides more surface area to attach muscles too. The pelvis is also fused. The longer pelvis makes the legs look longer and the torso shorter.

Avians have a secondary pair of scapula that sits on either side of the spine. This second pair rests below the first, these act as ‘sockets’ for the wings. The primary scapula or the ones that control the arms are slightly smaller and tilted compared to the flightless. This makes more room for the secondary set, the one more avian-like one that extends further down the back. They also have a slight protrusion of bone above the socket to stop the wing humerus from overreaching.

The wings and shoulders, since they’re not connected can move independently to one another. The arms, however, can disrupt the movement of the wings, when flying full keel, as in flapping to maintain height the arms must be moved forward over the chest. When gliding they can be moved into a more comfortable position.

The chest consists of the furcula (wishbone) and coracoid (collarbone), which, together with the scapula (see below), form the pectoral girdle. The side of the chest is formed by the ribs, which meet at the sternum (mid-line of the chest).

The shoulder consists of the scapula (shoulder blade), coracoid, and humerus (upper arm). The humerus joins the radius and ulna (forearm) to form the elbow. The carpus and metacarpus form the "wrist" and "hand" of the wing, and the digits are fused together. The bones in the wing are extremely light so that flighteds can fly more easily.

The hips consist of the pelvis, which includes three major bones: the ilium (top of the hip), ischium (sides of hip), and pubis (front of the hip). They meet at the acetabulum (hip socket) and articulate with the femur, which is the first bone of the hind limb.

The upper leg consists of the femur. At the knee joint, the femur connects to the tibiotarsus (shin) and fibula (side of the lower leg). The tarsometatarsus forms the upper part of the foot, digits make up the toes. The leg bones of avians are the heaviest, contributing to a low centre of gravity, which aids in flight. An avian's skeleton accounts for only about 16% of their total body weight

 

 

** [7.7] Musculature system **

All the muscles (Including the wing muscles) are intertwined and stitched together, creating new muscles to support their flight. Most avians have dozens of different muscles, mainly controlling the wings, skin, and legs. The largest muscles in an avian are the pectorals, or the breast muscles, which control the wings. They provide the powerful wing stroke essential for flight. The skin muscles help avians in its flight by adjusting the feathers, which are attached to the skin muscle and help the flighted in their flight manoeuvres. There are only a few muscles in the trunk and the tail, but they are very strong and are essential for an avian. The pygostyle controls all the movement in the tail and controls the feathers in the tail. This gives the tail a larger surface area which helps keeps flighteds in the air.

The muscles are designed to take large amounts of strain, specifically the stress of flight. Their muscles also contain the huge amounts of mitochondria needed to create and sustain the energy required for flight. More oxygen can be absorbed quicker, so they can remain conscious during highly energetic stints. Their muscles and tendons are also more flexible, this is to helps the wings to move quickly and efficiently into the proper flight positions without straining the rest.

**Notes for the Chapter:**

> Hey, ho, pseudoscience.


	9. [8] Senses

** [8] Senses **

** [8.0] Sight **

Eyesight is an avian’s most critical sense and the one it relies on the most for flight. They have a thicker retina than most mammals and their eyes are slightly larger than what would be considered in proportion to their head size. Avians have much denser rods and cone packed on the retina, giving them superior vision in both black-and-white and colour.

Avians can see a very large number of colours. Not only are avians able to perceive colours as well as parts of the ultraviolet spectrum that are invisible to most animal’s eyes, but they also have better visual acuity to determine subtle differences between similar shades of colour, gradations that most animals are not able to discern.

Some avians use the ultraviolet wavelength 300–400 nm specific to tetrachromatic colour vision. A typical avian eye will respond to wavelengths from about 300 to 700 nm. Most avians have retinas with four spectral types of cone cells that mediate tetrachromatic colour vision. The four cone types and the specialization of pigmented oil droplets give avians increased and more advanced colour vision than that found in mammals. Avians also utilize their broad-spectrum vision to recognize other avians, and in sexual selection.

Diurnal avians that are most active during the day have the best colour sense. Perceiving different colours is less crucial for naturally nocturnal avians, and many avians that are most active at night have a greater number of rod cells in their eyes instead, which allows them to capture more light and see better in low light conditions, though they may not see colours as clearly.

Where avians' eyesight really excels is in the perception of motion and detail. Avians can see small motions or tiny details 2-3 times better than apes, which can help them see movement below and around them easier or see incoming obstacles in the sky (such as another avian). In many avians, the eyes are positioned slightly further apart on the head, giving them an equally slighter wider view, though avians of prey have them placed close together and owls even closer together.

Because their vision is so critical, avians have an inner nictitating membrane that helps protect their eyes and cleans them frequently. During a fight, avians often spread their wings to protect their eyes, and when attacking, they know instinctively to go for the eyes of their adversary, normally with their talons and claws.

Most avians ‘circle’ move their head in circle or in other directions to gain a better view on what they’re looking at. Their varied head movements help them judge the position and distance of things around them, essentially, to triangulate on objects. Owls are the most extreme when it comes to circling, other avian do it rarely, in small movements, or never do it.

 

 

** [8.1] Smell **

The sense of smell is the least developed sense for most avians. Most avian species have very small olfactory centres in their brains, and they do not use smell extensively.

There are some avian species, however, that have much better-developed senses of smell. Vultures, kiwis, honeyguides, albatrosses, petrels, and shearwaters all use their keen sense of smell to locate food sources in more primitive times. These avians can often smell food from great distances, even when the odour may not be noticeable to any other avian species.

 

 

** [8.2] Touch **

Touch for avians is a vital sense, particularly for flight. Avians are incredibly sensitive to changes in air temperature, pressure and wind speed, and those changes are transferred down the feathers to extensive nerves in the skin. Mutual preening is an important part of primal courtship behaviour for many avian species and it may be related to a sense of touch as well since the avians are manipulating one another's feathers. No feathers, however, actually have nerve endings, they just transmit touch to the skin.

Avians have fewer nerves in their legs and feet, which makes them less sensitive to extreme cold and allows them to perch or stand on icy or hot surfaces without difficulty, however all avians have tiny pads on the end of each toe to ‘feel’ something when they walk and make sure it’s not dangerous. Some avians have extremely sensitive touch receptors in their fingers as well. Using touch to ‘see’ an object is something most avians do, the sensitive nerve ending here also make preening pleasurable for both avians.

 

 

** [8.3] Taste **

Carnivores, or animals who eat only meat as part of a normal diet, typically have fewer taste buds. Avians have around 3,000 taste buds in total.

Sour and salt tastes can be pleasant in small quantities, but in larger quantities become increasingly unpleasant to taste. The sour taste can signal rotten meat, and other spoiled foods, which can be dangerous to the body because of bacteria which grow in such media. Additionally, sour taste signals acids, which can cause serious tissue damage. Avians have a reduced ability to taste salt.

If an avian eat too much meat, they get too much salt. This can throw the ionic mechanisms into chaos, which includes about every function of every cell. Avians need to balance their salt intake with their water intake. To do this, avians have taste receptors for water. Avians may not perceive salt very well, but taking in salt makes their water receptors much more sensitive. This means water will be more pleasant to drink after eating meat. This mechanism makes avians want to drink more water after eating meat so that salt concentrations don’t get too high.

The bitter taste is almost universally unpleasant to avians. This is because many nitrogenous organic molecules which have a pharmacological effect on avians taste bitter. Avians avoid bitter tasting items as the tongue interprets them as rancid and rotten meant. this manner, the unpleasant reaction to the bitter taste is a last-line warning system before the compound is ingested and can do damage.

Sweet taste signals the presence of carbohydrates in solution. No avian can taste sweet flavours, they simply lack the proper taste buds. Meat isn't sweet and as this is the main diet for most avians the sweet taste buds are unnecessary.

The savoury taste signals the presence of the amino acid L-glutamate and triggers a pleasurable response and thus encourages the intake of peptides and proteins. The amino acids in proteins are used in the body to build muscles and organs, transport molecules (haemoglobin), antibodies, and the organic catalysts known as enzymes. These are all critical molecules, and as such, it is important to have a steady supply of amino acids, hence the pleasurable response to their presence in the mouth.

Avians can also taste adenosine triphosphate, a molecule that supplies energy to every living cell. It's present in meat, which is why avians can taste it.

 

 

** [8.4] Hearing **

Hearing is an avians' second most important sense and their ears are horse-shaped to focus sound. The ears are located slightly behind and below the eyes, and they are covered with soft feathers – the auriculars – for protection. The confusingly named ear tufts of many owls and other avians, however, have nothing to do with hearing.

Avians hear small frequency ranges, but they have much more acute sound recognition skills inside it. The hearing range is most sensitive between 1 kHz and 4 kHz, but their full hearing range is roughly 20 Hz to 20 kHz, with higher or lower limits depending on the avian species. Under ideal laboratory conditions, avians can hear sounds as low as 12 Hz and as high as 28 kHz, though the threshold increases sharply at 15 kHz in adults. Avians are especially sensitive to pitch, tone and rhythm changes and use those variations to recognize other individuals, even in a noisy flock. Avians also use different sounds, songs and calls in different situations.

**Notes for the Chapter:**

> I gotta work out how to make links work in the next chapter ∠( ᐛ 」∠)＿


	10. [9] Abilities

** [9] Abilities **

** [9.0] Intelligence **

Avian intelligence is the intellectual prowess of avians, which is marked by complex cognitive feats and high levels of motivation and self-awareness. It enables them to remember descriptions of things and use those descriptions in future behaviours. Avians possess the cognitive abilities to learn, form concepts, understand, apply logic, and reason, including the capacities to recognize patterns, comprehend ideas, plan, solve problems, make decisions, retain information, and use language to communicate. Intelligence enables avians to experience and think.

Anatomically, avians (the 10,000 species of which are the direct living descendants of, and so are, theropod dinosaurs) have relatively large brains compared to their head size. The visual and auditory senses are well developed in most species, while the tactile and olfactory senses are well realized only in a few groups. Avians communicate using mainly visual signals as well as through the use of calls and song.

Many avians follow strict time schedules in their activities. These are often dependent upon environmental cues. Some avians also are sensitive to day length, and this awareness is especially important as a once used cue for migratory species. The ability to orient themselves during migrations was attributed to avians' superior sensory abilities, rather than to intelligence.

 

 

** [9.1] Basic abilities **

[9.1.0] Running and walking

An avians legs and feet are designed to grip and move along rounded surfaces (such as branches) or uneven surfaces were their feet can curl and find grip. Flat surfaces normally lead to problems with grip and balance, however rarely so much as it disrupts normal life.

 

_ [9.1.0.0] Walk _

When walking their long legs lead to an exaggerated stride length. Their head and chest normally compensate for the sway, so they can remain in roughly the same position as an avian walks.

[How avians walk](https://78.media.tumblr.com/00e6500f1f9748b4ee62fc6ac5022883/tumblr_mpf1s8oh7p1qeoalpo2_400.gif)

 

_ [9.1.0.1] Run _

Most avians simply don’t run. When they need to run they’ll fly instead.

When they do run there’s not much difference between a walk and a run except it speeds up. At speed avians can cover large distances with long strides, they can easily maintain balance as their talons can grip the ground as they run. However, this run is only seen in a few different avians species.

Most avians don’t have the power or structure in the legs to support this type of run instead they’ll hop-run. Instead, they’ll shift their legs and hips to the side slightly, which direction is avianal choice (but still facing forward). They’ll push themselves up with the first foot, so they leave the ground. In faster or longer runs both feet will leave the ground. The back foot will then land just behind where the front foot was positioned (just as the front foot leaves). There’s always significant head and upper torso movement sue to bouncing up and down.

Some avians will run quadrupedally if they absolutely need to get somewhere fast without flying. Whether they run palms out or on the knuckles is choice since all avians have thicker skins there.

While it’s not as fast as the other type of running and it's defiantly more energy intensive they can still reach good speeds. (It’s why they fly not run.) The average avian can only keep up a full hop-run for a few minutes. It’s best used in small bursts. The second type of running described is mostly how avians shuffle and move along branches and other landing areas only adapted to be faster and to cover more ground. A jog is somewhere in between the two

An average avian with a hop-run can only reach speeds of around 15 – 20 mph. Avians who can normally run can regularly travel larger distances at a faster rate, around 22 – 35mph. Ostriches can naturally reach extremely high speeds of 40 – 50mph, however avians who can run normally, and train professionally, can have a chance of reaching these speeds also.

[How avians run on all fours](https://78.media.tumblr.com/f58e09c6030b2d2d4e5b1fab41326d56/tumblr_mpf1s8oh7p1qeoalpo5_400.gif)

 

[9.1.1] Climbing

The talons on an avians feet and the claws on their hands are mainly used for capturing, killing, and holding prey. However, their sharpness and curved points mean that most talons can get a relatively good grip on any surface, enabling the avian to climb or at least hold themselves to something.

While few avians have the pure muscle and talon strength to force themselves up a steep/vertical surface using their wings can help. Wing-assisted incline running allows most avians to run up steep or vertical inclines by flapping their wings, scaling greater inclines than possible through running alone.

However, this can only be used when there’s enough room for their wings to manoeuvre. Some avians are also simply too large, so you’ll mostly find small avians scaling walls and nature to get to a good vantage point.

 

[9.1.4] Internal clock

Circadian rhythmicity is present in the sleeping and feeding patterns of animals, including all avian species. There are also clear patterns of core body temperature, brain wave activity, hormone production, cell regeneration, and other biological activities. In addition, photoperiodism, the physiological reaction of avians to the length of day or night, and the circadian system plays a role in the measurement and interpretation of day length.

Avians have an incredibly sensitive circadian rhythm and can normally closely estimate real times without outside help. The shortening of days and the light their exposed to changes biological reactions. Without such a sensitive system avians would find it difficult to become sexually active at all.

 

[9.1.5] Sleep

Unlike mammals that enter a state of relatively complete unconsciousness while sleeping, avians can more intimately control their sleep. Avians often use unihemispheric slow-wave sleep (USWS), literally sleeping with one eye open and only half their brain resting. The other half of the brain is alert, able to note danger if needed. The more protected and safe an avian feels when sleeping, the more likely they are to sleep deeper, while if the situation may be precarious or they are stressed and anxious, they will sleep more lightly and is more likely to use USWS. Some long-flight avians such as swifts or albatrosses even use USWS in flight to sleep in the air without landing.

Sleeping in a flock is something many avians feel comfortable doing. Many flighteds, particularly small passerines such as chickadees, tits and blue-avians, will sometimes choose to roost together in specially built roosting houses; confined spaces to share body heat and feel more comfortable together. Even larger flighteds can make use of these buildings

When avians sleep, they protect vulnerable body parts surrounding themselves with their wings. An avian’s fluffed up feathers create insulating air pockets that help it keep warm, and by tucking feet and hands into their body and surrounding themselves with their wings, less body heat is lost. When an avian completely covers themselves with their wings they’re also able to breathe air warmed by their own body heat.

Another adaptation avians have for safe sleep is the construction of their feet and legs. A flexor tendon contracts the avian's toes and talons at all times, the tendon only releases when they want it to, it’s natural position being locked and tight, however, this is easily done. This means the automatic, at rest position of the foot is for the talons to be tightly locked around a perch, making it impossible for an avian to fall while sleeping, except in the rare circumstances they may fall asleep on flat ground not gripping anything.

Avians are able to ‘power nap’ during the day, however, and can catch up on sleep on longer days whenever they are in a safe, secure spot for a nap. Whilst most avians prefer using their round beds at home, all can get by sleeping standing up or perched. A few prefer it.

 

 

** [9.2] Advanced abilities **

[9.2.0] Magnetoreception

Primitive avians that had to navigate across continents had an extremely useful tool at their disposal–an internal compass that pointed unerringly towards magnetic north. While it’s not used for migration anymore it’s still an important feature of them orienting and directing themselves in their everyday life.

Light-sensing cells in their eyes convey the crucial message to a special visual centre of their brain, called cluster N. Special proteins called cryptochromes in the avians’ eyes may mediate this light-dependent magnetic sensing. Light hitting the proteins produces a pair of free radicals, highly reactive molecules with unpaired electrons. These electrons have a property called spin which may be sensitive to Earth’s magnetic field. Signals from the free radicals may then move to nerve cells in cluster N, ultimately telling the avian where north is.

The eyes sensitive state lasts only as long as the magnitude and direction the field stays constant.


	11. [10] Non-language Communication

** [10] Non-language Communication **

** [10.0] Body language **

Body language is a type of non-verbal communication in which physical behaviour, as opposed to words, are used to express or convey information. Such behaviour includes facial expressions, body posture, gestures, wing movement, eye movement, touch, and the use of space. Body language does not have grammar and must be interpreted broadly, instead of having an absolute meaning corresponding with a certain movement, so it is not a language like sign language.

In a community, there are agreed-upon interpretations of particular behaviour. Interpretations may vary from country to country, or culture to culture. On this note, there is controversy on whether body language is universal. Body language, a subset of nonverbal communication, complements verbal communication in social interaction. In fact, some researchers conclude that nonverbal communication accounts for the majority of information transmitted during interavianal interactions. It helps to establish the relationship between two flighteds and regulates interaction but can be ambiguous.

 

[10.0.0] Facial expressions

Facial expression is integral when expressing emotions through the body. Combinations of eyes, eyebrow, lips, nose, and cheek movements help form different moods of an individual (example happy, sad, depressed, angry, etc.).

Avians can adopt a facial expression voluntarily or involuntarily, and the neural mechanisms responsible for controlling the expression differ in each case. Voluntary facial expressions are often socially conditioned and follow a cortical route in the brain. Conversely, involuntary facial expressions are believed to be innate and follow a subcortical route in the brain.

Facial recognition is often an emotional experience for the brain and the amygdala is highly involved in the recognition process. The eyes are often viewed as important features of facial expressions. Aspects such as blinking rate can be used to indicate whether an avian is nervous or whether they’re lying. Also, eye contact is considered an important aspect of interavianal communication. However, there are cultural differences regarding the social propriety of maintaining eye contact or not.

 

[10.0.1] Body postures

Emotions can also be detected through body postures. Body postures are more accurately recognised when an emotion is compared to a different or neutral emotion. An avian feeling angry would portray dominance over the other, and their posture would display approach tendencies. Comparing this to an avian feeling fearful: they would feel weak, submissive and their posture would display avoidance tendencies.

Sitting or standing postures also indicate one’s emotions. An avian sitting till the back of their chair leans forward with their head nodding along with the discussion implies that they are open, relaxed and generally ready to listen. On the other hand, an avian who has their legs and arms crossed with the foot kicking slightly implies that they are feeling impatient and emotionally detached from the discussion.

 

[10.0.2] Gestures

Gestures are movements made with body parts (example hands, arms, fingers, wing, head, legs) and they may be voluntary or involuntary. Arm gestures can be interpreted in several ways. In a discussion, when one stands, sits, or even walks with folded arms, this is normally not a welcoming gesture. It could mean that they have a closed mind and are most likely unwilling to listen to the speaker’s viewpoint. Another type of arm gesture also includes an arm crossed over the other, demonstrating insecurity and a lack of confidence.

Hand and wing gestures often signify the state of well-being of the avian making them. Relaxed hands and wings indicate confidence and self-assurance, while clenched hands and tight wings may be interpreted as signs of stress or anger. If an avian is wringing their hands or shuffling and fluffing out their wings, this demonstrates nervousness and anxiety.

In most cultures, the Head Nod is used to signify 'Yes' or agreement. It's a stunted form of bowing - the avian symbolically goes to bow but stops short, resulting in a nod. Bowing is a submissive gesture, so the Head Nod shows they are going along with the other avians's point of view.

 

[10.0.3] Breathing

Body language related to breathing and patterns of breathing can be indicative of an avians mood and state of mind; because of this, the relationship between body language and breathing is often considered in contexts such as business meetings and presentations. Generally, deeper breathing which uses the diaphragm and abdomen more is interpreted as conveying a relaxed and confident impression; by contrast, shallow, excessively rapid breathing is often interpreted as conveying a more nervous or anxious impression.

 

[10.0.4] Ear positions

Turned out to the side: The avian is asleep or relaxed and may not be attuned to what's going on around them. You don't want to march up to them and pat them because they may be startled and react by attacking you.

Turned back: If the ears are pointed backwards but not pinned, it often means they’re listening to something behind them, they may be deciding whether to run away or turn around and check out the sound. When combined with a fanned tail or other signs of tension in the body, turned-back ears may be a precursor to pinned ears.

Rapidly swivelling: Ears that are flicking back and forth are a sign that the avian is in a heightened state of anxiety or alertness. They may be trying to locate the source of a frightening sound or smell, or they may be overwhelmed by too many stimuli.

Pinned back: Aggressive and dominant, normally accompanied by growls and hisses. This is normally a precursor to an attack, whether it be by talons or teeth.

Pinned down: Unlike when the ears are pinned back, pinned down ears mean nervousness and submission. Normally when they want to say sorry or avoid a fight.

Different directions: If the ears are pointing in different directions, it means their attention is divided between two things.

Low ears, different directions: If the ears are as low as they can go and point in different directions, it means the avian is in absolute terror. Especially so if the rest of their body conveys the same thing.

 

[10.0.5] Other physical movements

Stretching: Avians stretch to lubricate joints, to release tension, and primarily because stretching feels good. Many stretch one wing and a leg on the same side, then switch. This improves circulation and refreshes muscles.

Leaning forward, wings shaking: If the wings are quivering and the avian is on all fours they’re most likely getting ready for flight. An avian will intently at where they want to fly too, or just above them and will shuffle their wings; so, they catch wind quickly when they push themselves up. They only do this for a few seconds and many skip this entirely if they’re already on a high vantage point.

Quivering wings: An avian that’s shivering or has quivering wings may be frightened or overly excited.

Wing flipping: An avian will flip their wings up and down to indicate frustration, get attention, or indicate aggression. It may also happen during moulting when they're trying to align new feathers or get rid of old ones that may be hanging or ready to fall out.

Blushing: Avians will blush when embarrassed, extremely angry, or overly excited about something.

Flashing/Dilating Pupils: Flashing, dilating pupils can be a sign of aggression, excitement, nervousness, or pleasure. Pay close attention to other behaviours that accompany flashing/"pinning" pupils in order to correctly ascertain the reason for particular behaviour. In an avian that is exhibiting additional aggressive behaviours such as tail fanning, this behaviour means "Back Off!". Angry avians who give sufficient warning have very few second thoughts on biting and scratching. An avian may also exhibit this behaviour in response to another avian, animal, or item in the vicinity that they dislike.

Biting: An avian bite is a bite inflicted upon another avian. One or more successive bites, sometimes long with slashes from claws and talons, is often considered an avian attack. The majority of avian bites do not result in injury, disfigurement, infection or permanent disability. Another type of avian bite is the 'soft bite' normally displayed non-aggressive play, or playful aggression. Biting is obviously the most definitive form of showing displeasure. Biting avians often do so for a reason, though many raptors or more solitary avians will simply reach a social limit and feel the only way out is to bite. The avian may be feeling threatened, frightened, or startled. Biting can be anywhere from normal behaviour to rare aggression depending on the avian and their species.

Craning the Neck: This is simply an avian who is trying to see what activities are going on around them. Usually accompanied by a distinct widening of the eyes and the body being held very still.

Head Snaking: Characterized by the ‘snaking’ of the head from side to side in a fluid motion. It indicates excitement, a quest for attention, or be a display behaviour if it’s done during the mating season.

Preening: Preening is the activity that avians conduct to keep their feathers in top condition. It consists of running feathers through their preening bones from the base to the tip to straighten and clean them. Preening is also a social activity; avians will preen one another to remove feather sheaths that they cannot reach by themselves, it’s mainly done by friends and is used in steps to increase their relationships.

Wing Drooping: This is normal in hatchlings who have not yet learned how to hold and tuck their wings in. Likewise, avians who’ve just bathed may hold their wings down while drying. If neither of these situations is applicable, the avian may be overheated and attempting to cool themselves, or might be feeling poorly. Drooping wings accompanied by discomfort or refusal of flight is indicative of a sick avian.

Wing and Body Quivering: Quivering wings usually indicate fear, nervousness, uncertainty, or distrust.

‘Display’ Behaviour: This behaviour is characterized by a ruffling of the head feathers, fanning of the tail, wings extended in full display, a very distinct strutting walk, and is sometimes accompanied by dilation of the pupils, head bobbing, and loud vocalizations. These behaviours are usually brought on by attempts to attract a mate, or as a show of territoriality. These behaviours are never seen outside of mating season as their hormones aren’t fully active.

Crouch Stance: An avian that is crouching on all fours with their wings held high and tight, tail feathers flared, body feathers ruffled, and exhibiting pupil dilation is extremely scared. They’ll normally move away and hiss if approached, they’ll sometimes try to bite if backed into a corner. This stance will only last for a few seconds if surprised.

‘Defensive to the Death’: Avians that feel extremely threatened but cannot fly or otherwise escape will roll over onto their backs, with claws and talons extended ready to maul and mutilate. This posture is rarely ever shown in situations where it’s not needed, such as surprise.

Tail Bobbing: Tail bobbing, in and of itself, is not necessarily a sign of sickness. Some avians bob their tails while they are talking or vocalising. If the tail bobbing is evident only when the avian is inhaling/exhaling, then it could be a sign of sickness.

Tail Fanning: his behaviour is characterized as an aggression indicator, and denotes definite displeasure. An avian fanning their tail is upset and angry, and this behaviour is a prime indicator that a bite will almost certainly follow if you continue the activity that caused the fanning. This could be as simple as an unfavoured avian approaching. In some avians, it’s because they’re getting aggressive over others breaching their territory unasked.

Tail Wagging: This generally is a sign of contentment and happiness, especially at seeing a friend, or during an especially enjoyed activity. Consists of a quick ‘wag’ of the tail feathers back and forth.

Crest position: Almost all avians have crests they can control, the size can differ greatly though. A content and calm avian will normally have their crest held loose and down against the head. If it’s held back with the tip-tilted up, then their excited or something has caught their attention. A crest flared up can indicate aggression, fear, excitement, or happiness (if it’s put up momentarily) An aggressive and alarmed avian may leave the crest down.

 

Generally:

Aggression: Hackles (feathers on the back of neck) raised, head dipped, wings held out, one shoulder dipped.

Possessiveness: Mantling (wings out, tail fanned), turning back, side glances.

Nervousness: Feathers held tight, neck elongated, eyes wide, standing higher on legs, wings slightly out (ready to fly away), shifting weight, rapid glances.

Fear: Wings held out, feathers raised, shoulders raised, bouncing up and down ready to fly off at any moment.

Comfort: Feathers loose or poufy, one foot tucked up, rousing (shaking feathers), tail wiggling.

 

 

** [10.1] Vocalizations and calls **

Avians have a syrinx instead of a larynx found in mammals. It allows avians to produce any sound frequency because it vibrates in all directions, not just from left to right like mammals. Some also have 2 pairs of lips around their vocal cords, making it possible for them to produce 2 completely different songs or sounds simultaneously.

Avians vocalization includes both calls and songs. In non-technical use, avian songs are the avian sounds that are melodious to the ear. Songs (relatively complex vocalizations) are distinguished by function from calls (relatively simple vocalizations). The distinction between songs and calls is based upon complexity, length, and context. Songs are longer and more complex and are associated with courtship and mating, while calls tend to serve such functions as alarms, basic communication, and keeping members of a flock in contact.

In extratropical Eurasia and the Americas almost, all song is produced by male avian; however, in the tropics and to a greater extent the desert belts of Australia and Africa it is more typical for females to sing as much as males.

The avian vocal organ is called the syrinx; it is a bony structure at the bottom of the trachea (unlike the larynx at the top of the mammalian trachea). The syrinx and sometimes a surrounding air sac resonate to sound waves that are made by membranes past which the avian forces air. The avian controls the pitch by changing the tension on the membranes and controls both pitch and volume by changing the force of exhalation. It can control the two sides of the trachea independently, which is how some species can produce two notes at once.

The avian song has evolved through sexual selection, the quality of the song is a good indicator of fitness. Parasites and diseases can directly affect song characteristics such as song rate, which thereby acts as reliable indicators of health. The song repertoire also appears to indicate fitness in some species. The ability of male avians to hold and advertise territories using song also demonstrates their fitness.

Communication through calls can be between individuals of the same species or even across species. Avians communicate alarm through vocalizations and movements that are specific to the threat, and the alarms can be understood by others in order to identify and protect against the specific threat. The alarm calls of most species, are characteristically high-pitched, making the caller difficult to locate.

Individual avians are sensitive enough to identify each other through their calls. Many avians engage in duet calls. In some cases, the duets are so perfectly timed as to appear almost as one call. This kind of calling is termed antiphonal duetting. In territorial avians, they’re are more likely to countersing when they have been aroused by simulated intrusion into their territory. This implies a role in intraspecies aggressive competition.

Some avians are excellent vocal mimics. Vocal mimicry can include conspecifics, other species or even unnatural sounds. The functions of vocal mimicry are involved in sexual selection by acting as an indicator of fitness, help brood parasites, or protect against danger. Many avians are known to produce a snakelike hissing sound that used to threaten others or show fear.

Avians vocalisations are incredibly wide and equally varied. Most avian can also purr, growl, hiss, or click.

 

[10.1.0] Mating call

A mating call is an auditory signal used by avians to attract potential partners. It can occur in males or females. There are many different mechanisms to produce mating calls, which can be broadly categorized into vocalizations and mechanical calls. Vocalizations are considered as sounds produced by the larynx. Mechanical calls refer to any other type of sound that an avian produces using unique body parts and/or tools for communication with potential partners.

The use of vocalizations is widespread in avian species and are often used to attract mates. Different aspects and features of an avian song such as structure, amplitude and frequency have evolved as a result of sexual selection.

Large song repertoires are preferred by females of many avian species. One hypothesis for this is that song repertoire is positively correlated with the size of the brain's song control nucleus (HVC). A large HVC would indicate developmental success. Possible explanations for this adaptation include direct benefits to the female, such as superior parental care or territory defence, and indirect benefits, such as good genes for their offspring.

Avian calls are also known to continue after pair formation in several socially monogamous avian species. This increase is positively correlated with the partner's reproductive investment.

**Notes for the Chapter:**

> Wheyaho, please comment.


	12. [11] Activity

** [11] Activity **

Diurnality is a form of behaviour characterized by activity during the day, with a period of sleeping, or another inactivity, at night. Diurnality is a cycle of activity within a twenty-four-hour period; cyclic activities called circadian rhythms are endogenous cycles not dependent on external cues or environmental factors.

Crepuscular avians are those that are active primarily during twilight (the periods of dawn and dusk). This is distinguished from diurnal and nocturnal behaviour, where an avian is active during the hours of daylight or the hours of darkness, respectively. Some crepuscular avians may also be active on a moonlit night or during an overcast day.

Matutinal is were an avian is only or primarily active in the pre-dawn hours or early morning.

Nocturnality is the behaviour characterized by being active during the night and sleeping during the day.

While most avians are diurnal, for various avianal and social/cultural reasons some people are temporarily or habitually nocturnal, matutinal, or crepuscular. However, some species, like owls, are fully nocturnal.


	13. [12] Diet

** [12] Diet **

** [12.0] Type **

Avian diets are varied and often include nectar, fruit, plants, seeds, carrion, and various animals, including each other in more primitive times. Practically all avians are carnivores. A carnivore is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue. Carnivores may alternatively be classified according to the percentage of meat in their diet. Avians call all be placed into one of three carnivore types.

Almost all avians are hypercarnivores. Hypercarnivores are any avian which has a diet that is more than 70% meat, with the balance consisting of non-animal foods such as fungi, fruits, or other plant material.

Some avians are mesocarnivores, meaning their diet consists of 50–70% meat with the balance consisting of non-vertebrate foods which may include fungi, fruits, and other plant material.

Very few avians are hypocarnivores, but there are a few still around. Hypercarnivore avians normally consume less than 30% meat in their diet, the majority of which consists of non-vertebrate foods that may include fungi, fruits, and other plant material.

However, outside of the three main groups; Some avians, mainly Ocean-avians are considered piscivores, meaning they’re a carnivore that eats primarily fish. Other avians, exclusively humming-avians, are nectarivore, a nectarivore is an avian species which derives their energy and nutrient requirements from a diet consisting mainly or exclusively of the sugar-rich nectar produced by flowering plants. Even fewer are insectivores, those that mainly consume insects.

 

 

** [12.1] Hunting **

Raptors would kill avians or other animals for food by using their sharp claws, talons, and a powerful jaw. Hawks, eagles, and falcons hunt by sight. Those that hunted other avians would usually 'stoop,' meaning they dived at high speed on to prey during flight. The force of impact would knock the victim out of the sky. When hunting ground animals, raptors usually landed suddenly, pinning the victim to the ground with their talons and then worked to kill the prey quickly with claws and teeth, often repeatedly smashing the victims head into the ground. Then they’d drag it to a safe spot and eat it, tearing the flesh and organs out with sharp teeth, talons, and claws. Most owls hunted at night, using their acute hearing to locate prey. Owls' wing feathers are adapted for silent flight, allowing the owl to hear prey more easily. Avians who ate bugs would snatch them right out of the sky.

Of course, this was in more primitive times, before domestication and stores became a thing. All avians now just simply buy pre-killed prey in packages, to cook or eat straight from the pack.

Avians that live in a modern society don’t engage in hunting by their own power for survival. However, many avians still find themselves hunting inclined. Those avians often dispel hunting instincts and active prey drives by taking part in competitions were a rabbit or another animal is let loose and either the first one to attack and kill it wins or the one with the fastest time wins. Still, the animals are disposed of afterwards, sometimes taxidermized into a trophy for the winner, never eaten.

Other avians hunt purely for fun in the natural habitats of their prey, while this means shooting, fox hunts and otherwise, it also includes hunting by wing. Though all require a permit in almost all countries.

Those who live off the grid, such as indigenous people still traditionally hunt, catching, killing, then eating the prey. However, unlike others who hunt for fun indigenous people often hunt for survival. Here hunting is considered a natural skill and is passed on to younger generations.

Just because most avians feel hunting instincts and have a high prey drive doesn’t mean that they know how to hunt. They can’t do it properly if they’ve not been taught properly, and often end up hurt or worse.

 

 

** [12.2] Food items **

[12.2.0] Common food items

Food items such as beef, fish, goat, lamb, pork, ham, deer, sausages and some seafood are all considered common food items and can be found in most retail stores and restaurants. These foods are cheap and are produced in mass from domesticated animals.

Things such as seed, seafood, nectar, vegetables, and fruit could be considered uncommon for some avians but the main food of others.

Any food items avians eat can be eaten raw or cooked since their stomach can handle raw meat.

 

[12.2.1] Uncommon items

Uncommon food items are normally acquired from smaller more specialised food farms. They can also be acquired in small amounts from the wind if the food it too hard to acquire in captivity. Fish, whale, camel, various reptiles, horse, kangaroo, fruits, wolf, bat, certain types of deer, and plant material for avians who eat more vegetable matter.


	14. [13] Reproductive behaviours

** [13] Reproductive behaviours **

** [13.0] Season **

All avians have a breeding season, a time where all avians come into heat and reproduction becomes possible. For almost all avians species, outside of breeding season, males are considered borderline or completely sterile. Arousal is hard fought for both genders and generally, they’re not concerned with sex or romantic pursuits. The breeding season of each avian species is characterized in males by an increase in testosterone, exaggerated sexual dimorphisms and increased aggression and interest in females. Females will also be able to become pregnant.

The breeding season is the most suitable season, usually with favourable conditions and abundant food and water for breeding. Abiotic factors such as the timing of seasonal rains and winds can also play an important role in breeding onset and success. Whilst avians in modern times could easily raise and have children at any time there are still biological restraints from their more primitive days.

Most breeding seasons occur in and around springtime every four years.

 

Factors that affect the avian mating season include:

Geography: The farther north an avian’s breeding range is located, the later their mating season will begin. Some with later breeding season are much more active during it to account for the shorter productive breeding seasons, so they try to get more done quicker.

Water: In dry deserts or other arid habitats, the sudden appearance of water through seasonal storms or flooding can trigger the mating season. In those types of habitats, plants have evolved to quickly bloom when water is available, and those plants provide the necessary food for avians to raise chicks. As a result, many desert avians have more flexible mating seasons. If they move outside of the desert range their mating season will come into play if moving to a wetter country, however, their body will adapt and go back to normal soon after. They’ll become sexually active only after heavy rain.

Whilst many other factors used to play a part they no longer do in modern day.

 

!!!OOC: When in breeding season heat avians can easily continue life as normal if they want to. Their psychology is barely affected apart from the fact that becoming aroused is slightly easier. Males can get caught up in their instincts easier, but it will only be noticeably substantial if they actually do want to pursue a romantic partnership that year. If they don’t want to take part or find a partner that year both males and females can simply skip it and not take part in any mating rituals (though their plumage will still change). ~~Unless you want to write weird PWP then go right ahead, sure.~~

 

** [13.1] Selection **

[13.1.0] Courtship displays

A courtship display is a set of display behaviours in which avians attempt to attract a partner. These behaviours often include ritualized movement (‘dances’), vocalizations, mechanical sound production, or displays of beauty, strength, or agonistic ability.

Some avian species will try to find someone of their own species nearby home, some areas set up meetups. They’ll display to them there. Courtship displays are only ever shown in the species breeding season, otherwise, they simply sexually or romantically orientated enough to search out a partner. Outside of breeding season, it can be hard for avians to accomplish arousal either.

Some breeding seasons are placed far apart, or the displays don’t interest other species. So, finding and impressing partners outside of an avians own species can be hard if not impossible. While sex and children can be accomplished among practically all species there’s a heavy stigma over interspecies relationships.

Homosexual relationships are out of the ordinary, enough to turn eyes. But very few have a stigma over it and it’s generally acceptable.

 

Singing: Singing is one of the most common ways avians attract mates. The intricacy of the song or the variety of different songs one avian can produce help advertise its maturity and intelligence – desirable characteristics for a healthy mate. Singing can also define the boundaries of one avian’s territory, warning off competition. For some species, only one gender (usually males, or cock’s) will sing, while other species may create a duet as part of their bonding ritual

Displays: Flamboyant plumage colours and elaborate displays of prominent feathers or body shape can show off how strong and healthy an avian is, advertising its suitability as a mate. Peafowl are one of the best-known avian species for their stunning display with the males’ extensive upper tail covert fan. Other avians may use subtle changes in posture to show off their plumage to the best effect, such as raising a crest or flaring their wings.

Dancing: Physical movements, from daring dives to intricate sequences including wing flaps, head dips, or different steps can be part of a courtship ritual. In many species, the male alone will dance for his female (or hen) while she observes his actions, while in other species both partners interact with one another. Dance mistakes show inexperience, weakness or hesitancy and would likely not lead to a successful partnership

Preening: Close contact between male and female avians (or the same sex for homosexual couples) can be part of the courtship rituals to help diffuse their normal spatial boundaries and aggression. The avians may lightly preen one another, sit with their bodies touching or otherwise lean on one another to show that they are not intending to harm their partner. Though this is the same type of interactions between close friends and family.

Avianality: After all the flair and attention-grabbing of the females sometimes the male just doesn’t have a avianality that meshes with the females or the reverse. He has to have something apart from looks for the female to be interested in.

 

_ [13.1.0.0] Male / Cock display _

In most avian species, the male is the sex that initiates courtship displays in sexual selection. Performing a display allows the male to present his traits or abilities to a female. Mate choice, in this context, is driven by females. Direct or indirect benefits are often key deciding factors in determining which of these males acquire the opportunity to reproduce and which do not.

Direct benefits can be seen due to the expression of preference. Females can raise their own fitness if they prefer to respond to particular types of signals, independent of costs and certain benefits associated with mating. For example, choosing to mate with males that produce more localized signals would incur less of an energetic investment for a female as she searches for a mate.

Indirect benefits are benefits that may not directly affect the parents' fitness but instead increase the fitness of the offspring. Since the offspring of a female will inherit half of the genetic information from the male counterpart, those traits she saw as attractive will be passed on, producing an offspring that is potentially more fit.

In other species, males may exhibit courtship displays that serve as both visual and auditory stimulation. For example, the male Anna's humming-avian and Calliope humming-avian perform two types of courtship displays involving a combination of visual and vocal display - a stationary shuttle display and dive display.

In some species, males initiate courtship rituals only after having sexual intercourse with the female. Courtship may even continue after copulation has been completed. In this system, the ability of the female to choose their mate is limited.

 

_ [13.1.0.1] Female / Hen display _

Female courtship display is less common in avians as a female would have to invest a lot of energy into both exaggerated traits and in their energetically expensive gametes. However, situations in which males are the sexually selective sex in a species do occur. Female displays are common in lesbian couples and single lesbians who want to find a partner.

 

_ [13.1.0.2] Male-male (Cock-cock) fighting _

Many males will sometimes fight over the same female. While in some species she will now have a choice of many and will decide which over how they treat her, their avianality, how they look and many other factors. However, if the same situation occurs in other species the two or males will try to compete against each other.

Sometimes it will be aggressively displaying to one another, trying to prove that they’re better. It’s normally accompanied by attacks; these attacks are rarely serious and mainly a show of power.  Others will outright attack each other without displaying, also rarely serious.

In more primitive times the winner would be rewarded with the female. Though in modern times the female still has a choice on whether she thinks this male is worth it. Sometimes she goes for the one that lost or another male entirely.

This is the same in female displays, only reversed

 

 

** [13.2] Mating habits **

Avians being such a long-lived species don’t go into heat every single year. They only start going into heat around the age of 5 (58). After that, they go into heat every four years until around the age of 26 (201). Most avians who have chicks normally care for them for around 43 years. Sometimes avian have chicks in back to back mating cycles but this is uncommon. Most avians have around three to four chicks when they do get pregnant, they then spend the rest of their time caring for them. The most times an avian can raise chicks is thrice due to the time, energy, and toll they take on both parents, particularly the mother. Each breeding season after is used to bring the parents closer together and renew bonds by showing off their colours and status. Males do not produce sperm if they have chicks present so the chances of another conception during these times is incredibly rare.

 

Ninety-five percent of avian species are socially monogamous.

The shortest pairings pair for at least the length of the breeding season and chicks birth. The male will normally then leave next breeding season where he will find another partner and do the same. Occasionally they will remain longer than four years, but this is uncommon.

Other monogamous avians will remain together until their chicks grow and leave the family. After that, they’ll start to drift apart naturally unless they decide to raise more chicks. Sometimes avians will leave after their children grow and they’ll find another avian to do the same with, they normally remain in contact with their previous love.

If the two do not wish to split the relationship can be saved rather easily. These relationships are called Multiple-Monogamy/Monogamous, as they can remain romantically unique to one another but sexually active with others.

Others will mate, raise children together and after that, they’ll remain together until they die. These avians are exceptionally loyal to one another and infidelity and divorce are extremely rare. Normally the only thing that will part them is death.

 

Other mating systems, including polygyny, polyandry, polygamy, polygynandry, and promiscuity, also occur. Females are generally the ones that drive partner selection, although, in the polyandrous phalaropes, this is reversed: plainer males choose brightly coloured females.

Males in these mating systems will normally seek two or three different females to mate with. After that, they’ll all remain with each other either permanently or until the chicks are grown. Female avians in these groups normally only have one or two chicks instead of the normal three to four.

Sometimes one female will have more than one male. She’ll normally raise between five to six chicks at one time since the large family can help with raising a large number of chicks.

Others have open relationships to fulfil natural sexual needs of their polyamorous species all while staying with one another romantically, like monogamous avians.

 

Same-sex couples will normally form a temporary threesome with the same species of avian but of a different sex, the female will only leave once she’s had the child. This is normally cheaper than in-vitro fertilisation, though just as tricky to come by for obvious reasons.


	15. [14] reproduction

** [14] reproduction **

Avian reproduce by Ovo-Viviparity. Embryos that develop inside eggs remain in the mother's body until they’re ready to hatch. The embryos have no placental connection with the mother and receive their nourishment from a yolk sac. They’re born in live-birth like normal mammals.

The only changes that the female will go through is in the first month of nesting. She'll become increasingly irritable, stressed, and will become more active and will find themselves sleeping less. It’s her partner's duty to keep her calm, normally by mutual preening sessions.

It's very rare for one species of avian to bare offspring from a different species of avian. It’s normally around a one in one thousand chances of a successful reproduction. The differences in core temperatures and chromosome counts are the reason. It is possible, but a successful conception and birth is extremely rare.

However, the species the avian chick takes more after is depended on whose genes are dominant. Sometimes The pigment in the feathers of the offspring will be abnormal to the actual avian species. Sometimes physical traits are mixed up. But sometimes a chick will look exactly like one species, sometimes these chicks can have a normal life without prejudice affecting them.

 

 

** [14.0] Gestation **

When inside the womb yolk surrounds the embryo like a soft shell, however, the membrane on the inside is thicker to keep the embryo safer. The ‘egg’ incubates from the mother’s own core body temperature. After ‘hatching’, while still in the mother, secretions and unfertilized egg yolks nourish chicks.

Avians go through a relatively short gestation period, normally no longer than four months. Each chick must share the mother’s womb with two to four other chicks If they grew too large it would be too big for the mother to support, which is why avian chicks are all very small. The short gestation period also means the chick will be born before they start to severely weigh the mother down, stopping her from flying.

Since avian chicks are very small and light, the female doesn't get too big, just in case she needs to fly.

 

 

** [14.1] Birth **

Birth happens around the fourteenth week of pregnancy in most cases. However, some pregnancies will last slightly longer or shorter times. Female avians have everything set up in a way where the chick will be birthed quickly, however, these ‘fast births’ can be exceptionally painful.

Chicks are so early, so they don’t become large enough to greatly affect the mother's weight. If she became too heavy, especially around the stomach it would offset her weight and stop her flying. This could be deadly as should couldn’t get away from any predators. It also means the responsibility of the chick is quickly shared among the family group upping its survival rate. It stops the pregnancy from having large effects on the mother that might stop her from caring for her child.

By being born so early means that they’re very small, around the size of an orange, and vulnerable. But with two fully flighted and aggressive parents, this shouldn’t be a problem. Their childhood is greatly extended by this very quick birth.

**Notes for the Chapter:**

> I mean, who even reads stuff like this? Who writes stuff like this?


	16. [15] Breed types

** [15] Breed types **

** [15.0] Mongrel **

Mongrel, as insultey as it sounds isn’t actually all that negative. A mongrel is simply a normal avian who is the child of two other avians. Mongrels make up almost all the world’s population.

 

 

** [15.1] Pedigree **

Pedigree avians are avians who are deemed ‘perfectly imaged’. Meaning such things as perfect; colouring, amount of feathering, height, wing size, feather positioning, or proportioning.

An avian registry, also known as a herd book, studbook, or register, is an official list of pedigree avians within a specific breed whose parents are known. Pedigree avian are usually registered by their parents when they’re still young.

Pedigree avians are commonly found in pigeons, where there are several different pedigrees of pigeon all with different standards. They’re normally referred to as ‘show pigeons’ and are paid to simply stand and show off in competitions. Those who are heavily in-depth in ‘the showroom’ often setup sex and reproduction with others in the register, so they’re children can follow in their steps.

‘Show avians’ and their immoral ways of arranged marriage or sex is considered prostitution and is illegal in some countries, though very few. It’s sometimes considered unethical due to the fact that some pedigree breeds have inherent physical conditions than make their functional lives worse (extremely broad chest, triangle shaped wings, long irritable feathers on the ankles etcetera.) It’s also under scrutiny for catering to paedophile ethics and the sexualisation of minors, since pedigree avians who’s parents are already in the business are often put on show as soon as all their downy is gone.

 

 

** [15.2] Hybrid **

Hybrids are the rare result of two different species of avian having a child together, whether it be a duck with a falcon or flamingo with blue tit. Successfully having a Hybrid child is a one in a thousand chance, as most avians are not exactly matched to create a child and must have a bit of luck that all their genetics match up just right. There's also such a thing as a 'triple Hybrid' where a Hybrid adult has a child with another avian, their child will be three different types of avian, these are exceptionally rare. There's also such a thing unofficially known as a 'Double-Done Hybrid' that occurs when either a Triple Hybrid has a chick with another avian or two Hybrids have a chick together, being four different types of avian. There are only a few hundred known Double-Done Hybrids in the world.

Hybrid children and adults are victims of severe speciesism and prejudice. 62% 0f all Hybrids end up committing suicide before or just after puberty and their first heat. Many more are killed in hate crimes. Many are segregated and most are forcefully neutered by the government so they cannot have more chicks like them.

They can be legally refused medical service, education, jobs, or housing with no reason. While some countries such as England are trying to take steps to improve their quality of life most are not, some support this opinion and believe it’s the duty of the parents not to have a hybrid chick and their fault when they do. Even in places that are trying to improve it’s a slow process of changing avians, particularly religious avians, mindsets.

**Notes for the Chapter:**

> We're nearing the end now :)  
> If you like this check out my profile where I'm currently doing one for realistic mermaids. That one's not going to update as quickly as It turns out saying 'I'll add art later' means art won't be added very quickly heh. So I'm doing art as I write the chapters on that one.


	17. [16] Lifespan

** [16] Lifespan **

Avians have an incredibly dense and taxing brain. This brain needed to control and power the complexities of walking and running, usage of hands, and the most important tool; flight. When chicks are born their born with large amounts of Cerebrospinal fluid, this stops them from acquiring brain damage due to rough flying with their parents. As they grow, and their brain grows along with them the Cerebrospinal fluid begins to be drained by the body as the brain grows.

 

**0 (Eo=0 to 10) –** Chicks are born completely featherless and rely on their parents to keep them warm and safe. This continues until around the age of 1. At eleven, hatchlings will begin to grow downy feathers all across their body to keep them warm and camouflaged. It’s only here avian parents can start leaving the hatchling by themselves for extended periods of time.

**1 (Eo=11.6) –** At the age of eleven hatchlings have all their down and their brains can control walking and basic function of the hands and wings. By the time their fifteen they normally have good control of both. Here they only rely on their parents to keep them fed and carry them to higher ground. They’re normally around 4.3 ft. Their sagittal crest is practically fully grown to protect them from any bump of fall.

**2 (Eo=23.2) –** At seventeen the brain will start to recognise the wings as part of their body. They have finer motor control of all their limbs, especially their hands around this time. They can normally begin hunting on the ground as most still have a walking ability some will lose over better balance in flight. The downy feathers on the body will be replaced with full feathers first, normally around two years after they first start to moult. The moulting will then travel from the base of the wings to the tips, the primaries and tailfeathers are last to moult and grow. This occurs three to four years after they first start. It’s also around this time their fangs, claws, and talons will grow. They can normally protect themselves around this time and can accomplish gliding flight with new finer control over their wings.

**3 (Eo=43.8) –** At the age of 3 almost all avians should be able to accomplish full flight, their wing muscles strengthened by the previous years of gliding. Normally their talons, claws, and fangs are sharp, but not fully grown. If they haven’t already left their parents once they could glide they will now. Here they’re considered a full adult, but are not sexually mature yet so cannot give consent.

 

**5 (Eo=58) –** Avians don’t go into their first heat until around the age of 5. In the wild this left plenty of time for an avian to establish a territory before needing to worry about sex, it’s mostly the same with avians today. Letting them find a steady job and house before sex. Their sagittal crest also starts to shrink allowing greater room for growth in the brain (though avian never fully lose their sagittal crest as it is still used to protect the brain.)

**23 (Eo=166.8) –** An avians feathers will start to dull here, their bones and muscles will also become frailer. However, they can still fly, and their breeding plumage still comes in during mating season. The feathers will only half grow in, being shorter than they should be or in more washed out colours.

**24 (Eo=178.4) –** Avians will stop going into heat during breeding season. New feathers will start to damage earlier and since they don’t moult for breeding season no new feathers grow in to replace the damaged ones, leading to a rattier appearance. They lose colour and break easier too.

**26 (Eo=201.6) –** At this stage reproduction becomes completely impossible. Females do not produce any more eggs even during breeding season. Males stop producing sperm, where before they could be harvested with a simple procedure since they still had them they just wouldn’t be used during intercourse, now males do not have any.

 

In prehistoric times the life expectancy was around the same as modern day, this is most likely due to less contact with other avians so there’s a smaller chance of spreading diseases, though this is only one theory. During the last few hundred years the lifespan shrank due to rampant diseases and several plagues such as the black death, avian influenza, the rabies epidemic, the Brahmae virus outbreak, the malaria infection, etcetera. Many other long-lasting health disorders were also avian-created, bad diets, lack of flight and sunlight in cramped cities, medical intervention that only made things worse etc. With new medical advances, vaccines, the opening of cities, higher regulation food, it slowly allowed avians to live their ‘full’ lifespan of around 220 years again.

An average avians lifespan is around two hundred and twenty years (220y) or 28. However, avians can live for around 240 if they in very good health and don’t have any disorders. A lot of avians die before even the age of two hundred, however. The lifespan varies from country to country but rarely more than one or two decades above or below the expected lifespan.

The flightless are roughly the same but slightly sped up. They normally reach their goals a year or two earlier than the flighted so can be considered adults quicker. It’s been theorised that it’s because they don’t have to learn the finer points of flying so skip a lot of growth time avian need. Most flightless are considered adults much earlier than avians and reach their first heat much sooner, however their lifespans on average are a decade less than those who fly.

Note. All avians before the age of 3 have a severe fear of heights. This is their body telling them they’re not ready to fly so shouldn’t even consider trying it. When the fear subsides that’s their body now telling them they should be able to fly and glide at this point. This fear will sometimes return much later in life once an avians bones start to frail and their wings become ratty, this is their body telling them they’re probably too weak to fly and once again shouldn’t try it.

 

Young ˅˅˅

11 = 1 (at 7 downy feathers will grow)

23 = 2 (Good control of limbs, downy will moult, can glide)

43 = 3 (full flight, normally leaves parents)

46 = 4

 

58 = 5 (Sexually mature)

69 = 6   /

81 = 7   /

92 = 8   /

104 = 9   /

116 = 10   /

127 = 11   /

139 = 12   /

150 = 13   /

162 = 14   /                                     }} Adult

174 = 15   /

185 = 16   /

197 = 17   /

208 = 18   /

120 = 19   /

132 = 20   /

143 = 21   /

155 = 22   /

 

Old ˅˅˅

166 = 23 (Feathers will start to dull, and breeding season plumage will start coming in only washed out)

178 = 24 (Avians will stop going into heat)

190 = 25

201 = 26 (Reproduction becomes impossible as males no longer create any sperm and female eggs)

213 = 27

224 = 28

**Notes for the Chapter:**

> Originally their ages were only around fifteen years ahead of ours, but I found that even that’s not a large enough difference. Ages began to become confusing since the lifespans were similar. So, I made the age differences more extreme, so they could be easier to understand.
> 
> Tbh I'm thinking of just scrapping this whole age thing and fitting it into a human timespan so whatever.


	18. [17] Sickness Behaviour

** [17] Illness **

** [17.0] Sickness behaviour **

Sickness behaviour is a coordinated set of adaptive behavioural changes that develop in ill individuals during the course of an infection. They usually (but not necessarily) accompany fever and aid survival. Such illness responses include lethargy, depression, anxiety, breakage of feathers, malaise, loss of appetite, sleepiness, hyperalgesia, reduction in preening and failure to concentrate.

Sickness behaviour is a motivational state that reorganizes the organism's priorities to cope with infectious pathogens.

****

** [17.1] Disease(s) **

A disease is a particular abnormal condition that affects part or all of an organism not caused by external force and consists of a disorder of a structure or function, usually serving as an evolutionary disadvantage. Disease is often construed as a medical condition associated with specific symptoms and signs. It may be caused by external factors such as pathogens or by internal dysfunctions, particularly of the immune system.

In avians, disease is often used more broadly to refer to any condition that causes pain, dysfunction, distress, social problems, or death to the avian afflicted, or similar problems for those in contact with them. In this broader sense, it sometimes includes infections, isolated symptoms, deviant behaviours, and atypical variations of structure and function, while in other contexts and for other purposes these may be considered distinguishable categories.

Death due to disease is called death by natural causes. There are four main types of disease: infectious diseases, deficiency diseases, genetic diseases (both hereditary and non-hereditary), and physiological diseases. Diseases can also be classified as communicable and non-communicable.

 

[17.1.0] Disease

The term disease broadly refers to any condition that impairs the normal functioning of the body. For this reason, diseases are associated with dysfunction of the body's normal homeostatic processes. Commonly, the term is used to refer specifically to infectious diseases, which are clinically evident diseases that result from the presence of pathogenic microbial agents, including viruses, bacteria, fungi, protozoa, multicellular organisms, and aberrant proteins known as prions. An infection that does not and will not produce clinically evident impairment of normal functioning, such as the presence of the normal bacteria and yeasts in the gut, or of a passenger virus, is not considered a disease. An infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease. Non-infectious diseases are all other diseases, including heart disease and genetic disease.

 

 

** [17.2] Types by body system **

[17.2.0] Mental

Mental illness is a broad, generic label for a category of illnesses that may include affective or emotional instability, behavioural dysregulation, cognitive dysfunction or impairment. Specific illnesses known as mental illnesses include major depression, generalized anxiety disorders, schizophrenia, and attention deficit hyperactivity disorder, to name a few. Mental illness can be of biological or psychological origin. It can impair the affected avian’s ability to work or study and can harm interavianal relationships.

 

[17.2.0] Organic

An organic disease is one caused by a physical or physiological change to some tissue or organ of the body. The term sometimes excludes infections. It is commonly used in contrast with mental disorders. It includes emotional and behavioural disorders if they are due to changes to the physical structures or functioning of the body, such as after a stroke or a traumatic brain injury, but not if they are due to psychosocial issues.

**Notes for the Chapter:**

> Meh


	19. [18] History

** [18] History **

** [18.0] Evolution **

The Troodon, from the late cretaceous, is well known as one of the first ‘missing links’ to be found in support of evolution. Though it is not considered a direct ancestor of modern avians, it gives a fair representation of how flight evolved and how the very first avians might have looked. The skeleton of all early avian candidates is basically that of a small theropod dinosaur with long, clawed hands, and numerous feathers.

Species in-between Troodon and the first flying, or gliding, dinosaur has rows of spines protruding from their back and spine. Over generations these spines migrated to a more horizontal position and the skin between them strengthening. Volanimus is the much later relative of Troodon. The spines on the back of the previous species now function and single jointed skin flaps that can be controlled. While Volanimus and its relatives may not have been very good flier’s due to their body shape, they would at least have been competent gliders, setting the stage for the evolution of life on the wing.

The evolutionary trend among avians has been the reduction of anatomical elements to save weight. The first element to disappear was the bony tail, being reduced to a pygostyle and the tail function taken over by feathers. Spinactroectro is an example of this trend. While keeping the clawed fingers, perhaps for climbing, it had a pygostyle tail, though longer than in modern avians. A large group of avians evolved into ecological niches similar to those of modern avians and flourished throughout the Mesozoic. Though their wings and arms resembled those of many modern avian groups, they retained the clawed wings and an extended snout with multiple of the same type of teeth. The loss of a long tail was followed by a rapid evolution of their legs which evolved to become highly versatile and adaptable tools that opened up new ecological niches.

The Eocene saw the rise of more modern avians with a more rigid ribcage with a carina and shoulders able to allow for a powerful upstroke, essential to sustained powered flight. Another improvement was the appearance of an alula, used to achieve better control of landing or flight at low speeds. They also had a more derived pygostyle, with a ploughshare-shaped end. The skin flaps and spines in the ‘fan’ slowly retracted as they were replaced with colourful feathers that allowed for greatly control in flight, and self-powered flight.

Flight was extremely useful for avian now and then, this is due to many large ground beasts that disallow any other competing predator from arising on the ground, avians filled the niche in the sky. It allowed them their own area away from any other creature other than other avians. It allowed them, and still allows them, to strike from the sky quickly and escape equally quickly without a possibility of being chased. It also ensured their chicks 100% safety from predators, just put the nests somewhere no creature can get to and no reasonable creature would ever want to.

As avians started to spread over the world each species started to increasingly diversify, becoming more specialised in the areas they settled down in. Avians never made a transition to full bipedalism. Whilst it was useful on the ground and in some areas in canopies the quadrupedal stance was, and in most cases still is, a much easier and balanced stance for them. However even partly bipedal it allowed them to free up their hands along with their prehensile feet.

Their long ages were caused by the sheer amount of time and resources needed to be sacrificed to their proper growth and brain power needed to fly and think intelligently. Their long childhood was able to be sustainable due to avians being apex predators in most areas, able to fly away with their child at the drop of a penny. The flightless are well known for being more aggressive and short lived to combat their lack of flight.

**Notes for the Chapter:**

> Ta-da THE END. Thank god.

**Author's Note:**

> \- Some of this information has been directly taken and modified from Wikipedia to better fit this document. Parts of Wikipedia documents have been used alongside personal writing, creations, and small sections from other sites that allow their work to be used.


End file.
